m3u is just a playlist..You can use a burrrn or foobar and drop a playlist-m3u so he will actually play the playlist..
But to avoid confusion couse you probably dont use a playlist...just delete that and listen those mp3 files,its a simplest thing..

But to listen them in car???Check on your car stereo..in a manual or its written on front panel if its support mp3??if it does...youre in luck..just burn a regular data disk with every software you like..If it doesent support mp3??just burn those mp3 like audio cd with every(almost every)software..
Example eac,feurio,nero,bao,foobar..whatever software you use..
For audio aplications i really recomend eac.feurio,burrn and allmighty foobar of course
