Passcode -I don’t know it.
How can I reset it or find out what it was?
Question marked as
The only way to find out wha it was would be if you wrote it down or otherwise made a note of it somewhere.
If you forgot a passcode that you changed within the last 72 hours, see the following for instructions: Temporarily use your old passcode when you forget your new passcode on iPhone or iPad - Apple Support
Otherwise, there is an Apple article that explains what to do if you have forgotten an iPhone or iPad passcode. Click on the following link: If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support
If that is not an option, you will need to use a computer. See:
If you forgot your iPhone passcode - Apple Support
or
If you forgot your iPad passcode - Apple Support