Stolen iPad

A lost or stolen iPad cannot be traced or located via its Serial Number or other identifiers. The IMEI is only useful in having the associated device barred, by your Carrier, from using Cellular service.

Start here:

Locate a device in Find My on iPad - Apple Support

Here is Apple’s advice for lost or stolen devices:

If your iPhone, iPad or iPod touch is lost or stolen – Apple Support

Use the Find My app to locate a lost or stolen device – Apple Support

If the Find My iPad feature was enabled prior to it being “misplaced”, then if active, you would stand a good chance of locating it. 

However, if the feature was not activated prior to being misplaced - or the iPad has been inactive for more than 24 hours, the last known location will not be available - and the opportunity to use technical means to recover the iPad have been lost.

only the police in your country really, if they present a warrant to the carriers they can force them to triangular track the device if it's online, it's at times used in missing person cases, and the cost of cause would be substantial so doubt many countries law enforcements would put it in motion over theft.

in some countries when one report the device stolen to the police if one present the IMEI they will have all carriers operating in the region block the device, other places you have to get your carrier to do that yourself