How do I find the owner of a found iPad?

Apple cannot (and will not) assist with reuniting a lost device with its owner. Unless a found device has an active network connection - and the owner has marked the device as lost with a visible message in-screen, you’ll not be able to identify the owner or any contact information.

The best advice that can be offered is that you hand the device to your local authorities - along with a description of where and when the device was found. Alternatively, if found at a public transport hub, they will likely have a lost a found department with whom you can deposit the found item.

You will not be able to unlock or use the iPad. Without both the Passcode and AppleID credentials that secure the device, the iPad is and will forever remain useless to you.

No. Although the owner may post a lost message on the iPad. Keep it powered. Turn it into the local lost and found or police.