Hello and welcome to Apple Support Communities, Alyssa!
I understand you're not able to get your iPhone to work with your car stereo. I'd be happy to provide information to help you troubleshoot this.
Use the steps in the following article: If your iPhone, iPad, or iPod doesn't connect to or work in your car
"If you connect using USB playback
- Restart your device and your car.
- Make sure that your device is unlocked and on the Home screen.
- If possible, try to connect using another cable or USB port. Check your car owner's manual to learn how to connect an Apple device.
- Check your charging port for any debris or damage. Make sure that your charging cable is inserted fully into the port.
- Update your device.
- Install any firmware updates for your car stereo.
- Try playing audio from a different app. If you can't play audio from a third-party app, contact the app developer for help. If you can't play audio from an Apple app, contact Apple Support."
Thank you for using Apple Support Communities.
Enjoy your day!