I forgot my apple ID

See: If you forgot your Apple ID  https://support.apple.com/en-us/HT201354  and

If you forgot your Apple ID password https://support.apple.com/en-us/HT201487

You also can use Having trouble signing in/iForgot https://iforgot.apple.com/password/verify/appleid

You also may need to see If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485

If you can't recover your credentials and you are the rightful owner, you will need to have an extenuating circumstance (e.g., have your original purchase receipt with its serial number on it) and to contact Apple support. Post back for support options.

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Otherwise your iPad will be useless to you.

If necessary, if you are the original owner, contact Apple ID Support. Apple Support will need to see the original purchase receipt with the serial number/paperwork.

Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.  (Link doesn’t always load)   

Get Support      Work through the screens to get a chat option. 

Apple Support schedule phone call

https://twitter.com/AppleSupport