For better security, set a passcode that must be entered to unlock iPad when you turn it on or wake it. Setting a passcode turns on data protection, which uses your passcode as a key to encrypt Mail messages and attachments stored on iPad with 256-bit AES encryption. (Other apps may also use data protection.)

Set or change the passcode

  1. Go to Settings , then depending on your model, tap one of the following:

    • Face ID & Passcode

    • Touch ID & Passcode

    • Passcode

  2. Tap Turn Passcode On or Change Passcode.

Information sourced from: https://support.apple.com/en-au/guide/ipad/set-a-passcode-ipad997daf9f/ios