ASUM returns the inertial properties of an area (a "surface body" created with MAPDL). There are no MAPDL "solid model" entities in models created by Mechanical, so if your model was created in Mechanical I would not expect ASUM to work.
This is old code but I think it might still work.
The parameters returned by the *GET command in the code above are described in the MAPDL Help:
I hope this helps!