Mkv to Mp4 Converion using ffmpeg using c# not working

Question

I recently working on webApplication where i need to play the videos capture by the

security camera,so tha i need to convert mkv file mp4 for supporting all browser. I decided to install FFMPEG to convert a MKV(Source file:- https://www.appsloveworld.com/2018/10/sample-mkv-video.html) to MP4 which people say has almost no loss in quality, etc. However, when I try to convert a ~900MB MKV file it returns a 0kb MP4 file.Image

The line of code I use is "ffmpeg -i set.mkv -codec copy set.mp4"

but i'm getting error, you can find below