why my file is generated in ADLS like this 'part-00000-6feffff6-eef6-41ec-9d' even i mention the filename on adf

I used a Data Flow on adf for filter the column of dataset and stored the output on a filename.csv file as you can see on pic
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but in adls a new file generated with this name: part-00000-6feffff6-eef6-41ec-9da8-c10e671923df-

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I agree with @Gal Weiss that dataflow follows the spark way when writing to the files.

Adding to that answer, if you want to get it write to a single file, go to Sink settings-> File name option -> Output to single file and give your file name in it.

But for this, we need to set the partitioning to Single partition which slowdowns the dataflow execution time.

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This will write it to a single file in the same target folder like below.

This is a partition file,
I'm not familiar with the way your data flow works.
But if this is something that using spark or Hadoop, this is the way it saves files
It splites them to multiple partitions for simplicity of parallel processing.
In this case the name you assign will function like a directory name and the actual data is in the "part" files.
That is ok, if you will try to read the dataset using the same file name, the spark/Hadoop filesystem knows to look for the "part" files under it.

Lastly, the reason you have only one file is because of the way the data was partitioned before being written, or you have very small dataset and the default configuration is to use only one partition.