Skip iCloud

There is no way they could have done that without your iCloud ID and password.

If you got a message, email, phone call, etc. indicating your iPad had been found and responded to it, you probably fell for a phishing message and gave the thief your credentials.

You will never see that phone again.

If you mean that you did not sign into iCloud before it was stolen, you're out of luck. There is nothing anyone can do.

Report it to your cellular carrier and the police.