Add the names of the files to concatenate in a list (e.g., mylist.txt):

file 'file1.mp4'
file 'file2.mp4'

Then run this command and pass your list:

$ ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence