If you have forgotten the ScreenTime passcode, the procedures outlined within this link should resolve the problem:
If you forgot your Screen Time passcode - Apple Support
Since release of iPadOS 13.2, iPadOS introduced a mechanism whereby a forgotten ScreenTime passcode could be reset without wiping the iPad - this requiring the AppleID and associated Password that was used when the ScreenTime Passcode was set.
To reset a forgotten ScreenTime passcode on older versions of iOS/iPadOS, or where the AppleID credentials are not available, the iPad must be complete reset “as new”, losing all locally stored data:
Settings > General > Reset > Erase All Content & Settings
In this situation, you’ll not be able to restore your data from an iCloud or iTunes backup - as the forgotten ScreenTime Passcode is integral to the backup. Be aware that reseting the iPad will likely trigger an Activation Lock - again requiring knowledge of the AppleID credentials.
If you have forgotten your AppleID credentials, they can be recovered here:
https://iforgot.apple.com
More information about recovery of your AppleID and associated Password:
If you forgot your Apple ID - Apple Support
If you forgot your Apple ID password - Apple Support