I found an iPad it’s locked. How can I reset it

If the iPad disabled or Activation Locked, unless you can independently obtain assistance from the previous owner, the iPad is (and will remain) useless to you.

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 the original sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.

As you “found” the iPad - and it isn’t yours - you should hand it in to your local authorities, together with a description of where and when it was found.