Nobody can gain access to your iPad without successfully entering the correct device Passcode (presumably known only to you) - and for this, there are a limited number of tries before the iPad will automatically become disabled. As such a brute-force attempt to access the iPad, by guessing the correct passcode, is highly unlikely to be successful. Only if your device Passcode is known to whoever finds your iPad will any locally stored data be at risk of discovery.
iOS/iPadOS is architecturally designed to protect the owners data.
All locally stored data is encrypted; by design, the only copy of the encryption keys necessary to access local data are held within the Secure Enclave - the device security chip. The device Passcode unlocks the Secure Enclave, which in turn releases the encryption keys to the Operating System while the device remains unlocked.
If an incorrect Passcode is repeatedly entered, the Secure Enclave automatically wiped and the device disabled - an operation that erases all stored encryption keys. This is known as a crypto-erase. Once erased, all locally stored data is permanently beyond reach and cannot be recovered.
Given that you have already removed the iPad from your AppleID account - and therefore have no opportunity to locate or initiate a remote erase - as a precautionary measure you would be well advised to change your AppleID Password:
Change your Apple ID password - Apple Support
After changing your AppleID Password, you will need to sign-in again on any other devices that you still have in your possession.
