Making iPad secure for repair when it is unusable

If you cannot access the iPad and successfully enter a passcode, it is impossible to erase any locally stored data.

While you cannot erase or remove any data from your damaged iPad, this issue isn’t as concerning as it might first appear. Your iPad and its locally stored data has an encrypted filesystem. The encryption keys required to access local data are securely stored within the iPad security chip (the Secure Enclave). The only way to release the encryption keys, necessary to decrypt data, is to enter the iPad Passcode known only to you.

If you can’t enter the Passcode, neither can anyone else. No Passcode = no decryption = no access to data.

Even if the iPad is subsequently restored to running status, the Passcode will still be required. This cannot be brute-forced - as only a limited number of attempts are possible before the iPad becomes disabled - at which time the Secure Enclave is automatically erased - destroying all hope of ever accessing locally storage data.

Clearly you are able to access the iPad and its settings. As such, here is Apple’s guidance:

Get your iPhone, iPad, or iPod touch ready for service - Apple Support

Be aware that manual deletion of files or data whole the iPad remains connected to iCloud has implications for all other devices. Performing a full device reset will erase all data - without affecting other devices.