How to post data dropdown to server in flutter

I have a case where I want to send data to the server. here I have 3 bodies that must be sent, but I'm confused.

here the transcript_value key has 2 values, if number 1 is selected then it will send VALUE TRANSCRIPTS without sending SEMESTER and if number 2 is selected then it will send KHS and also SEMESTER (dropdown).

how to POST data to the server with two conditions as below

I'm confused about how to explain it but I hope you understand
Next I show the API and also the display on mobile

> in API

Create>> pengajuan-class.dart ( u can also create all your json to dart >>https://javiercbk.github.io/json_to_dart/ )

class pengajuanClass {
  String? status;
  String? code;
  String? message;

  pengajuanClass({this.status, this.code, this.message});

  pengajuanClass.fromJson(Map<String, dynamic> json) {
    status = json['status'];
    code = json['code'];
    message = json['message'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['status'] = this.status;
    data['code'] = this.code;
    data['message'] = this.message;
    return data;
  }
}

Create>> pengajuan-services.dart ( pengajuanClass need to be quick fix because u need import this class)

import 'dart:convert';
import 'package:http/http.dart' as http;


class transcriptValueServices {
	
  static Future<pengajuanClass> AddpengajuanService(
    String jenis_transkrip,
    String semester,
    String keperluan_cetak,
  ) async {
    try {
      final response = await http
          .post(
            Uri.parse(
              'your URL',
            ),
            headers: {
			// write all your headers
              'Content-Type': 'application/json',
              'Authorization': 'Bearer ***', // If u have a bearer write it or delete this.
            },
            body: jsonEncode({
              'jenis_transkrip': jenis_transkrip,
              'semester': semester,
              'keperluan_cetak': keperluan_cetak,
            }),
          )
          .timeout(const Duration(seconds: 30));
      var json = jsonDecode(response.body);

      if (response.statusCode == 200) {
        return pengajuanClass.fromJson(json);
      }
      return pengajuanClass(code: "999");
    } catch (e) {
      return pengajuanClass(code: "999");
      
    }
  }
}

U can call like this in click event >> ( dont forget to write async to click event example: onPressed: () async { } )
//"pengajuanClass" and "transcriptValueServices" need to be quick fix because u need import

pengajuanClass returnData = await transcriptValueServices.AddpengajuanService("selected data","selected data","selected data");

I hope it works ^^