3D model for milling of stone relief

I am looking for a freelancer to prepare a 3D model of a stone relief that will be a milled stone plate. The output file should be STL format. The final stone will have dimensions (LxWxH) of 200 mm x 200 mm x 20 mm. The minimum milling resolution is 3 mm. In the middle, there should be a through hole with a diameter of 20 mm. Attached draft example which should serve as a starting point for modeling.