How to transfer the id of a certain element to the backend after a click event?

I am working on a certain page write now on my project that is responsible for listing movies and after you click them it links you to a page where you can see all the information about the specific movie you clicked on, now I am using SQL on my database and one of my Ideas to that is to transfer the id of the element being pressed after I already taken care of assigning the right id's to the hyperlink that is being clicked on based on the movie you clicked on.My question is how do I take the id of what is being clicked, transfering it to the backend so that I will be able to pull the right information from the database according to that same id.
this is my code so far:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

namespace WebProject
{
    public partial class movie : System.Web.UI.Page
    {
        public string movieLister = "";
        protected void Page_Load(object sender, EventArgs e)
        {
            string fName = "contentDB.mdf";
            string tableName = "moviesTbl";
            string sqlSelect = $"select * from {tableName}";
            DataTable table = Helper.ExecuteDataTable(fName, sqlSelect);
            int length = table.Rows.Count;
            for(int i = 0; i < length; i++)
            {
                movieLister += $"<a href='moviePage.aspx' id='{table.Rows[i]["MOVIEID"]}'><div class='movie-container' ><img src='{table.Rows[i]["movieImageFile"]}'/><div><img src='favourites.png' /> {table.Rows[i]["rating"]}</div><p>{table.Rows[i]["movieName"]}</p></div></a>";
            }
            
        }
    }
}

this piece of code makes essentially a list of movies and assigning the correct id's relative to movie's description and sending it back to the page, the only thing is I need to know what to do in order to take the id of what movie has been clicked so that I will be able to transfer the correct information to the page from the data base.

I have tried approching multiple resources but none of them seemed to help.

As you did not post the page, I am assuming that you are simply spitting out the movieLister string like so {%= movieLister %} This should generate a tags in the format you use in your for loop like so:

<a href='moviePage.aspx' id='{table.Rows[i]["MOVIEID"]}'>
  <div class='movie-container' >
    <img src='{table.Rows[i]["movieImageFile"]}'/>
  <div>
  <img src='favourites.png' /> {table.Rows[i]["rating"]}
</div>
<p>{table.Rows[i]["movieName"]}</p>
</div>
</a>

There are 2 issues with this HTML for what you want

1. There are two closing div tags without an opening. This is likely a typo but will cause the rendering engine of the browser to get very confused (and likely the StackOverflow syntax highlighter as well)
2. While each link has the id attribute pointing to the movie id, that information is not part of the url that will be loaded when you click the link as it is not in the href attribute

To fix both of these I would update the outputed html to look something like this:

<a href='moviePage.aspx?id={table.Rows[i]["MOVIEID"]}'> <!-- Update this href to use the id as a query parameter -->
  <div class='movie-container' >
    <img src='{table.Rows[i]["movieImageFile"]}'/>
  <div>
  <img src='favourites.png' /> {table.Rows[i]["rating"]}
<div> <!-- update this tag -->
<p>{table.Rows[i]["movieName"]}</p>
</div>
</a>

Then you should be able to update your page handler like so (note I am on a MacBook and cannot validate this ASPX code as .NET Core/5+ uses Razor Pages only):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

namespace WebProject
{
    public partial class movie : System.Web.UI.Page
    {
        public string movieLister = "";
        protected void Page_Load(object sender, EventArgs e)
        {
            string id = Request["id"];
            string fName = "contentDB.mdf";
            string tableName = "moviesTbl";

            string sqlSelect = $"select * from {tableName}";
            if (id.Length() > 0)
            {
                sqlSelect += $" where id = {id}"
            }

            DataTable table = Helper.ExecuteDataTable(fName, sqlSelect);
            int length = table.Rows.Count;
            for(int i = 0; i < length; i++)
            {
                movieLister += $"<a href='moviePage.aspx?id={table.Rows[i]["MOVIEID"]}'><div class='movie-container' ><img src='{table.Rows[i]["movieImageFile"]}'/><div><img src='favourites.png' /> {table.Rows[i]["rating"]}<div><p>{table.Rows[i]["movieName"]}</p></div></a>";
            }
            
        }
    }
}

Important Security Notes

The above code is for demonstrating how to get the ID only. In production I would strongly suggest you either convert it to an int or parameterize it to avoid very simple SQL injection attacks.

I also strongly recommend you migrate to .NET Core/5+ and Razor pages as they make asking such questions here and on google much easier as they are self contained and easier to post the full source. Tim Corey on YouTube has great videos at all levels if you want to learn about Razor pages