How do I use my non cellular 2020 ipad with my iPhone to make a FaceTime call?

FaceTime calls can be made using your WiFi network connection.

Set up FaceTime on iPad – Apple Support

In absence of WiFi, it is then that you need an alternative network connection. If you have an iPhone - or other cellular phone - if your phone’s cellular plan permits hotspot/tethering, you can use your Cellular hotspot with your iPad.

How to set up a Personal Hotspot on your iPhone or iPad - Apple Support