How to convert camera and radar coordinates on the common plane

I am planning to do sensor fusion (camera and radar data). can anyone tell me how i can convert camera and radar coordinates on the common plane.

Hi. Can you elaborate what you mean by common plane?
I would recommend projecting them into lidar or birds-eye view perspective.

Common plane means same coordinate. As Ridar points are in world coordinate system (x,y,z) but camera image in (x,y) so how i can bring radar points in image plane? should i use render_pointcloud_in_image function??

Well, as the name indicates that method just renders things, it does not return them.
You should take a closer look at the NuScenes class. That method uses the map_pointcloud_to_image method (https://github.com/nutonomy/nuscenes-devkit/blob/master/python-sdk/nuscenes/nuscenes.py#L515) which does what you need.