npm install

brew install ffmpeg

1. Download the binaries at https://www.ffmpeg.org/download.html
2. Extract the files to C:\ffmpeg
3. Make sure C:\ffmpeg\bin is present and contains the ffmpeg.exe file inside
4. Add to the PATH environment variables

npm run convert -- --from=avi --to=mp4 --folder=/Volumes/Disk/Videos

This will take all .avi files from /Volumes/Disk/Videos and convert them into .mp4 there'll be a new folder /Volumes/Disk/Videos/mp4 with all of the converted files.

Make sure the path is absolute and not relational. Also you must have write access to the folder.