LG VX-8100

I have read several times that it's easy to convert mp3's to WMA's (want to do this so I can use playlists on my v07 phone) with Windows Media Player. I have version 10.0 of Windows Media Player, and can't find anywhere how to convert mp3's to WMA's. I feel stupid, since I know the solution is probably really obvious, however if anyone could help I'd appreciate it!