How can I back up my iPad when I can’t turn it on?

It is important to ensure that you have a backup of your devices before disaster strikes - not after.

If you are unable to power-on and successfully enter your device passcode, it is too late - and you’ll not be able to access or backup any locally stored data or files. Your iPad uses an encrypted file-system; your passcode unlocks the iPad security chip - and this allows data to be decrypted and accessed.

If the security chip cannot be unlocked with your Passcode, your data is [by design] beyond reach.

If the iPad does not turn on, it cannot be backed up.