If you have forgotten the ScreenTime passcode, one of the two procedures outlined within this link should resolve the problem:
If you forgot your Screen Time passcode - Apple Support
Unfortunately, in having an iPad4, your iPad is incapable of update to PadOS 13.x. As such, the Restrictions Passcode (now known as the ScreenTime Passcode) cannot be reset without wiping the iPad.
To reset a forgotten ScreenTime passcode on older versions of iOS/iPadOS, the iPad must be reset “as new”, losing all locally stored data. In this situation, you’ll not be able to restore your data from an iCloud or iTunes backup - as the forgotten passcode is integral to the backup.