Hiya and Welcome !!!
We need more info from you in order to help...
What do you have in your car for a player ?
Is it a CD player that is supposed to be compatible with .mp3 files as well as 'normal' CDA ?
Or, is it a BlueTooth system that is supposed to work with a BlueTooth compatible .mp3 player ?
Or.... What ???
p.s. You will notice that I have changed the original name of your thread/post...
Remember that the more clear you make your first post(s), the quicker you will receive (maybe) helpful answers !!!
Don't panic... I am sure someone here will come up with a fix for you... Once we know more about your gear !!!