How do I get data off iPad with damaged screen?

If your iPad cannot be successfully powered-on - and the Passcode entered - it is too late to create a backup. 

All locally stored data is encrypted; entering the Passcode unlocks the iPad security chip (the Secure Enclave) within which the encryption keys, necessary to access your data, are stored. If you can’t enter the Passcode, your data is beyond reach.

Your must create a backup before disaster strikes - not after.

Is there a reason you put this post in the Apple Pay community? Do you want it transferred to the iPad Community?