Hello Scot14.
Welcome to Apple Support Communities. I understand that you want to copy your iTunes playlist to a USB flash drive, so that you can upload the music to your car’s media center. I’m happy to help.
Please follow the steps in the section titled “Back up your library and media files” here: Back up and restore your iTunes library on your PC - Apple Support
Once you’ve done this, please follow the steps in your car manual or from the manufacturer of your car radio on how to transfer the playlist to your car’s media center.
Let me know if you have further questions.
Take care.