Resizing 3D model via points/mesh in AR

Recently, I saw video showing a prototype of an architecture app using AR.

I know that I need to use AR Ground place, but I don’t understand how to make two points in diagonally at the base of the room via UE, and then scale of 3d object will increase in the right proportions.

Could you tell me, please, how can I decide this issue?

Yours respectfully,