While perhaps counterintuitive, open the setup prompt from iPad settings - then cancel the setup. This should inhibit further prompts from appearing.
Setting-up ApplePay on your iPad can actually be very useful. While your iPad is not designed to be used in the same manner as your iPhone at point-of-sale terminals (the iPad lacks the specific hardware to support touch-less/proximity payments from the device), ApplePay can be used when accessing online stores - both streamlining and improving the security of the payment transaction.
When using ApplePay, your pre-configured payment/delivery address details are conveyed securely if needed - along with a one-time payment authorisation. ApplePay never reveals your actual Credit Card details to a merchant - and as such, your Credit Card details cannot be stolen or intercepted by a nefarious Bad Actor. The one-time purchase authorisation is just that; details cannot be cloned or repeated without your explicit participation.
In summary, setting-up ApplePay (should you choose to do so) facilitates fast an secure payments when (and if) you choose to use this facility.