New iPad won't pair with iPhone 13 Pro

Bluetooth pairing an iPhone with an iPad or a Mac is not supported. 

If you are attempting to use Handoff/Continuity or AirDrop, that does involve Bluetooth but the devices are NOT paired; Bluetooth just needs to be on and the devices in range of each other. The following may help with Handoff/Continuity issues: Continuity features and requirements for Apple devices - Apple Support

Also see Share files between your Mac and Bluetooth devices - Apple Support

And see the information in: Bluetooth: Why can't I pair my iPhone or … - Apple Community

I just got a new iPad, it will not pair with my iPhone 13Pro !

That is correct. An iPad will not pair with an iPhone or vice versa.