A file with an m3u extension, as I understand it, is simply a link to, or a list of, your mp3 files. In the Limewire library, click on one of your mp3 files and select 'explore' in the bottom left corner of the screen. This will open up the actual folder that contains your music files. Try dragging and dropping (or whatever you need to do...I've never put music on a cell phone) from this folder.

Hope this helps

Dano