Converting .vlc files to .mp3 format.
Converting VLC Playlists directly to MP3 Audio Files (.vlc to .mp3 conversion) is, per se, not possible, since VLC playlists do not contain any multimedia data. They are basically only references to multimedia files.
These files do not need to be converted to other formats. Should you, however, need to play the audio using a different software, try renaming the extension from VLC to MP3.
We are not aware of any (online) conversion solutions capable of converting VLC to MP3.
In a word, direct vlc to mp3 conversion is not possible.
So don't expect any so-called vlc to mp3 converter or vlc to mp3 free online conversion tool available.