ipad

This is the procedure to perform:-> What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

But, if the device is locked... you need to unlock it before proceeding. How is it locked?

Unlock 1 = Apple ID locked (Generic):-> If your Apple ID is locked or disabled - Apple Support

Unlock 2 = Apple ID locked (in AppStore&iTunes):->  If you see a message that says 'Your account has been disabled in the App Store and iTunes'

Unlock 3 = Passcode forgotten:-> If you forgot the passcode on your iPhone, or your iPhone is disabled

Unlock 4 = Activation Lock:-->  How to remove Activation Lock

Unlock 5 = Frozen device:--> If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

If you mean something different, please better specify your needs.

Regards

Giulio

As described, your iPad is perhaps Activation locked?

Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be turned off:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Turn off Activation Lock – Apple Support

As you will discover, unless you are the owner of the AppleID that was last used to activate the device, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.

If you have the necessary documentation, Apple have recently introduced a new portal though which you may be able to request release of an Activation Lock:

How to remove Activation Lock - Apple Support & start an Activation Lock support request.

However, recovery of the AppleID credentials should be possible…

If you have forgotten your AppleID or associated password, these can be recovered here:

https://iforgot.apple.com/

To recover your credentials, you’ll need access to any 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:

If you forgot your Apple ID - Apple Support

More information about recovery of your AppleID password:

If you forgot your Apple ID password - Apple Support

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/