I don’t know my 4 digit screen time code

The options will depend on if you are part of a Family Sharing plan. If you are and not the Organizer, it must be done by them.

If you are not part of a Family Sharing plan, then you can do this if when you set it up you allowed the option to use you Apple ID and Password as a backup in case you forget it:

1. Go to Settings > Screen Time. 
2. Tap Change Screen Time Passcode, then tap Change Screen Time Passcode again.
3. Tap Forgot Passcode?
4. Enter the Apple ID and password that you used to set up the Screen Time passcode. Forgot your Apple ID password?
5. Enter a new Screen Time passcode, then enter it again to confirm.

These options and more are available in this Support Article including a link to contact Apple if none of those work.

If you forgot your Screen Time passcode - Apple Support