Hello,
For a disabled iPad, or one for which you have forgotten the passcode, Apple provides different solutions depending upon the system version you are using and other criteria.
For devices with iPadOS 15.2 or later* you may be able to use the method in this support article: If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support
Here is a related video: https://www.youtube.com/watch/7s8-zLG9ySQ
If your device is still running iPadOS 15.1 or earlier, you will need to use the method in this support article: If you forgot your iPad passcode - Apple Support
You may also need to use this method if:
• your device is not connected to a cellular or Wi-Fi network (if you restart your device when you see "Security Lockout" on the Lock Screen, you won't be able to reconnect to a Wi-Fi network until your device is unlocked. Cellular devices will reconnect to a cellular network if you have active service).
• you do not have your Apple ID and password that you used to set up your device.
*These models, when running iPadOS 15.2 or later, do not require a computer:
iPad Air2, iPad mini4 (if updated)
iPad Pro
iPad Air 3rd generation and later
iPad (5th generation and later)
iPad mini (5th generation and later)
Here are resources if you are prompted for your username and password and have forgotten them:
If you forgot your Apple ID email address or phone number - Apple Support Note that typically this is an email address you use.
If you forgot your Apple ID password - Apple Support
If you do not have a computer, use this link Find Locations to find an Apple service location, or ask a friend if you can use theirs.
Whichever method you use will result in erasing the iPad. You can, however, restore it from a backup as described in this support article --> Restore your iPhone, iPad, or iPod touch from a backup - Apple Support