Sorry to hear that your iPad was stolen. Here are some suggestions on what you should do in your situation:
You won't be able to trace the serial number, but the steps in the link above may help. Good luck, and sorry again about your loss.
A device can only be traced if Find My has been turned on in iCloud on the device, the device is turned on, and it is connected to the internet. Tracking or tracing by serial number or any other means is not possible.
If the device has been stolen and the thief has restored it to factory condition, it will never appear in iCloud's Find My Phone system. A knoweledgable thief will wipe the device immediately so it cannot be traced.
Be sure to change all passwords associated with acconts on the iPad.
Apple (and no one else) can not assist (with serial number or iCloud) in finding a lost or stolen iPad.
Report to police along with serial number. Change all your passwords.
These links may be helpful.
How to Track and Report Stolen iPad
Reporting a lost or stolen Apple product
What to do if your iOS device is lost or stolen
iCloud: Locate your device on a map
Report Stolen iPad Tips and iPad Theft Prevention
How to recover a lost or stolen iPad
How to Find a Stolen iPad
What NOT to do if your iPhone or iPad is lost or stolen
Apple Product Lost or Stolen
Oops! iForgot My New iPad On the Plane; Now What?
If you don't know your lost/stolen iPad's serial number, use the instructions below. The S/N is also on the iPad's box.
How to Find Your iPad Serial Number
iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number