How to format internal memory to FAT32?

I want to listen music in my car through USB connection but my car system only reads fat32 memorycards and GS3 internal memory is in EXTFAT.... so I need to format my internal memory card to FAT32. How do I do it?

Also, how can I bacup my internal memory to pc?? i tried selecting files and copying them to pc but it always gives an error and closes. Thks!