Which SAP module is best for a mechanical engineer with no prior experience to work in an IT sector? I want to work with corporations. Is SAP Basis good enough?

Once you feel confident, you can join that course, because you yourself are the only person to decide as you have to learn it first.

You can work in any module. Learn it and you are good to go. But if you want to choose best module for mechanical engineer it is MM module material management.

Atos provides the course with some fees and highest package goes upto 10 Lakh Per annum for freshers.

But you can choose any one of your interest, all are good. Check for HANA , Basis , ABAP etc. Once you feel confident, you can join that course, because you yourself are the only person to decide as you have to learn it first.