The easiest way how you can convert various song playlists (such as .m3u or .m3u8) would be to load them up in some media player and save them to whatever format suits you.
The free and highly popular VLC player is excellent choice for this as a lot users already used it as default media player and have it installed on their computers, so simply resave the playlists to achieve m3u to m3u8 conversion.
Updated: July 7, 2023