Which 3D modelling software will be best for me? I am diploma Mechanical and I want to work in Qatar.

Basically it would depend on your experience with3D Modelling software's. If you are a beginner I would suggest you start with software's like Solid Edge. This is more easy to learn. If you have more experience I would suggest Pro-E which is one of the Professional3D modelling softwares that is used by most of the large industries in our sectors.