I HAVE BOUGHT AN IPAD FROM GUMTREE AND IT IS LOCKED CANNOT FOUND THE OWNER

Sorry, but you’re short of options. You should return the iPad to the Seller for a refund.

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, or unless you can secure the cooperation of the previous owner, you’ll not be able to defeat or bypass the Activation Lock. Without documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple won’t assist; there’s nothing that anyone here can do to help you.

The All Too Common SAD Reality of Buying … - Apple Community

You will never, EVER get this iPad to work for you!

Your only option? Return this locked device and attempt to get your money back, if you csn.

Failing that, please recycle this device responsible.

Next time, if you need/want an iPad with an up to date iPadOS with access to current, updated apps, then you really need to seriously consider a new iPad model OR a much, MUCH “newer” and less expensive, used iPad models, from better known, trusted sources, like Apple product/device retailers/resellers, capable of running the latest iPadOS versions.

There are plenty of newer, older iPad models that can run the latest, current versions of iPadOS.

Sorry & Best of Luck to You!