how do I share my iPad to my MacBook Pro with airplay

AirPlay, as a technology, does not support sharing of an iPad or iPhone display with another computer. A mac, with a compatible version of macOS, can use an iPad as an extended display using SideCar - or other third-party Apps such as Duet Display - but this does not work in reverse.

Use your iPad as a second display for your Mac with Sidecar – Apple Support

https://www.duetdisplay.com/

There are applications you can run on your Mac that can act as AirPlay receivers and display on the Mac Screen. One such app that I use occasionally is named Reflector from a company named Squirrels LLC. They are up to version 4, which I have not tried, but version 3 worked as advertised.