A:Answer You can use your mp3 player in your car if your car has an aux port. You will need a double aux cord. Just plug in the aux cord into the headphone outlet of the mp3 player and into the aux outlet of car. If it doesn't connect automatically, then go into the radio settings and select aux option. You could probably use the USB cable, but it has been my experience that the aux works better. Most mp3 players do come with a small USB cable, but not all. They are usually really small.