iPad Says Unavailable

“Unavailable” generally indicates that you (or someone else) has repeatedly failed to enter an incorrect Passcode. If you see a waiting period - and you know the Passcode - you can wait and try again. If the iPad Passcode is unknown, you’ll have no alternative other than to reset the iPad - which will unavoidably delete all locally stored data. The reset will also very likely trigger an Activation Lock.

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 introduced a 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, this isn’t necessarily the end of the story...

A close Family member or Executor, with the required supporting paperwork, can make application to Apple to be granted access to the Apple accounts of the deceased:

How to request access to a deceased family member's Apple accounts - Apple Support

Having recovered access to the AppleID account (and therefore the AppleID username and associated Password), Activation Locks can be removed. There are several routes to this, but for brevity, I’ll refer you to this support page:

Turn off Activation Lock – Apple Support

If the passcodes of any devices are unknown, the data stored on the device itself is now gone. That said, if the device has an associated iCloud backup, you can restore the backup data to the device. To do so, you would need to follow this procedure:

If you’ve forgotten the passcode on your iPad, or your iPad is disabled – Apple Support

You’ll need access to either a Windows PC (with iTunes for Windows installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of MacOS). At the end of the process, you’ll have the option to restore data from the backup.

If your intent is to wipe/reset the device(s) for reuse by a new user, you would be best advised to prepare them properly:

What to do before you sell, give away or trade in your iPhone, iPad or iPod touch – Apple Support