So I have a USB plug in my car so I've been loading my iTunes music on a jump drive and playing it through my stereo that way .. The thing is, my car will only read mp3 and a lot of my music on my iTunes is m4a or some random file name .. How do I convert my music to mp3? And is there a way to just be like, "Convert everything that's not an mp3 to mp3 at one time" or do I have to go file by file? Thanks