Destroyed - or damaged but running?
Unless you are able to successfully input your Passcode, you’ll not be able to access or backup any data from the iPad. If the iPad is running and you are able to input your Passcode, then backup remains technically possible. Generally you should create your device backup before disaster strikes - as retrospective attempts are perhaps very unlikely to be successful.
As to your supplementary question… disabling Find My on your iPad will not erase an existing iCloud backup - and neither will it inhibit creation or update of an existing backup subject to the provisions outlined above.