You need a converter go to google and type in m4a to mp3 converter. I have one burnt on disk somewhere , I'll try to find it.
As a matter of fact I use this one.
http://www.imtoo.com/wma-mp3-converter.html
With a snagged serial from
www.serials.ws
Just type in ImTOO in the search engine and grab one from the audio encoders on the bottom, one should work.