Why doesn't my itunes downloaded to a

My car radio/cd will not list the title name and song for the itunes that I bought and downloaded from the istore?

Is it in the type of download I am selecting or do I have to buy the CD hardcopy in order to read the title name currently playing.

I have a 2003 Nissan Altima with a BOSE 6 CD system.

I also have a 2007 Ford Elite with a 6 CD system.

Thank You.