If any kind of mpe to mp3 conversion is possible, it would be export of audio tracks from MPEG movies (usually .mpg but sometimes .mpe) and save the audio content as regular MP3 files, maybe for making ringtones or similar purposes. You can find more converter options under mpg to mp3 conversion entry.
But it might as well be a typo for different file type, so maybe recheck your search query.
Updated: July 21, 2023