Ok.
Head to www.icloud.com and sign in with the same Apple ID you've used on your iPad. Then click 'Find my iPhone'. In the devices list, your iPad should be listed. The devices list can be found by clicking 'all devices' at the top of the page. You can then remotely lock or wipe the iPad, or find out where it is in the world!
These instructions will only work if your iPad is connected to either wi-fi or a 3G/LTE cellular connection. Furthermore, if you did not enrol your iPad with 'Find my iPhone' these instructions will also fail to work.
Besides Find my iPhone, Apple offers no other way of recovering lost devices. Local Police is the best option.
More info here If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support