If you have forgotten the ScreenTime passcode, one of these two procedures should resolve the problem:
https://support.apple.com/en-us/HT211021
If your iPad is capable of supporting iPadOS 13.x, you should update to the most current version before attempting to resolve a forgotten ScreenTime passcode. The most recent iPadOS updates have introduced a new mechanism whereby a forgotten ScreenTime passcode can be reset without wiping the iPad. The current version is iPadOS 14.0.1.
To reset a forgotten ScreenTime passcode on older versions of iOS/iPadOS, the iPad must be reset “as new”, losing all locally stored data.
I hope this information is helpful to you in successfully resetting your forgotten passcode.