My new used car from 2005 has a CD that will not play an MP3 CD, but I can buy an adapter that will add an AUX input and a USB input to the radio. (Since the radio has a CD changer jack that is not in use, and this is designed for that shape of jack.)
Long after I ordered one for $18, it suddenly dawned on me that if it can't play an MP3 CD, it won't be able to play an MP3 file from a USB-connected flashdrive. That's true, is it not????
It's amazing how long it took me to think of this problem, at least a week.