If your iPad is disabled, or you have forgotten your iPad passcode, you’ll need to follow this process:
https://support.apple.com/en-gb/HT211078
You’ll need access to either a PC (with iTunes installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of MacOS). Use of a PC/Mac computer is unavoidable - but if you don’t have one of your own, that of a helpful friend or family member will suffice. Alternatively, your local Apple Store will be happy to assist.
You’ll also need your AppleID and associated password. If these have also been forgotten, they can be recovered here:
https://iforgot.apple.com
To recover your credentials, you’ll need access to one of the following:
- Your primary email address mailbox that corresponds with your AppleID
- Any of the secondary/recovery email addresses that should be configured for your AppleID account
- Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID
Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.
More information about recovery of your AppleID:
https://support.apple.com/en-us/HT201354
More information about recovery of your AppleID password:
https://support.apple.com/en-us/HT201487
When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:
https://appleid.apple.com
You also need to be aware that Apple ended update support for iPad3 in September 2016. Your iPad3 cannot be updated to iOS 10 or later versions, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS. The 32-bit architecture upon which the iPad3 is based is effectively obsolete.
Many App Developers have also dropped support for older devices and iOS versions preceding iOS11/12/13 - and have withdrawn older versions of their Apps from the Apple App Store, now limiting utility and usefulness of older devices. Subsequent to withdrawal of compatible Apps, you’ll not be able to (re)download or (re)install these Apps - and this limitation will affect you as all Apps currently installed on your iPad will be lost during the restore process.
If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model. Even the basic current iPad7 model supports current iPadOS 13.x - and has hardware specifications and capabilities that will vastly outperform your old iPad.
I hope this information is helpful - if only in clearly stating the limitations of your iPad3 and your available options.