Most of media players nowadays give users the tool for making their own playlists of either selected files or whole libraries. Such mp3 to pls conversion is actually not file conversion, more of creating a settings from a list of audio files. Plenty of various playlist formats available, but not all may be supported in every media player.
Open MP3 file Open PLS fileA music library management program - renamed to Helium (version 12) and replaced in 2016