How to Detect the Ground Plane and Place the Object in Three.Js

How to access the Ground plane detection in three.Js and when my phone will detect the Ground plane then the marker will appear ? or marker will be on my screen Only…

Have you checked the official example:

The other option is to use some 3rd party AR library that can detect the ground plane and return its properties (like, position, orientation, coefficients, etc). Then you can use these data to calculate the plane in Three.js space and place objects on it.

its not working