How to unlock my iPad forgot my iCloud

If you forgot your iCloud/Apple ID email address,

Follow: If you forgot your Apple ID email address or phone number - Apple Support (CA)

If you do not get luck still,

Your Apple ID might be included in some emails from Apple. Search your inbox for receipts as well as repair, support, or billing emails from Apple.

Also, Try to search in your browsers of another device for saved passwords. Ask your friends and family members if they have your email in their Facetime/iMessage history, also check on your old tax papers or resume if you can find your email ID.

Even if you do not get luck then,

You have to go another way, Activation Lock Removal.

Important Notes:

You must be the owner of the device.

Proof of ownership documentation is required. Proof of ownership must include the product serial number, IMEI, or MEID.

Your data on the device will be erased.

If Apple unlocks Activation Lock on your device, all files and data stored on your device will be permanently erased. Please note, restoring your device from a local backup will re-enable Activation Lock.

Submit ALR With Your Proof Of Purchase: https://al-support.apple.com/#/getsupport