I bought a iPad from someone and it says activation lock

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

https://support.apple.com/en-us/HT201365

https://support.apple.com/en-gb/HT201441

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 - and nobody here will be able to help you.

Sorry - but you’re short of options.

You seemingly got scammed.

Activation Lock is a theft deterrent, and wouldn’t be a deterrent if could be bypassed.

You need the Apple ID and password, or proof of original purchase and matching ID and a discussion with Apple.

The All Too Common SAD Reality of Buying a Used iPad/iPhone

Then, you bought a brick!

Without the aid of the person who sold you this iPad to you or able to contact the original owner of this iPad, you will never, EVER get this iPad to work for you.

No one here will be able to help you. Apple WILL NOT help you.

Activation lock cannot be circumvented/worked around.

If you can, attempt to return this iPad from where you purchased and attempt to get your money back!

If no joy, recycle this device responsibly.

It will never work for you!

If you must purchase older, used iPad models, DO NOT look at anything older than a 2014 iPad Air 2 or 2015 iPad Mini 4.

Both of these models are the oldest iPad models that the up and coming iPadOS 14 will support, in the Fall of 2020.

If you must purchased used devices from unknown, untrusted sources, you must ask A WHOLE LOT more questions of the iOS device seller, ask for more photo/images, ask if the iPad has user/iCloud activation lock and ask for photos/images/short video proof, ANY POSITIVE, VISUAL PROOF, that such an iPad has been reset to factory settings and shown proof of the iOS device's start up screen showing the animated, moving, multi-language “Hello” Welcome to iPad screen.

If the iOS device seller is unwilling to do all of this to show you that the iPad, in question, is ready to use with no barriers to new user activation and use, pass on the iOS device and look at other iOS device sellers, elsewhere, that will be more accommodating and willing to answer and supply such image and video proof.

Sorry & Best of Luck to You!