Step to Solid object using Autocad
First open Autocad and ensure that you are in 3D Modeling Mode..
Now under Insert selct Import option
Select your Step file and press Open
Autocad will take some time to Import the file and once it as finished importing click on the path of
impoted file which is underlined
Now you have converted the Step file into solid body in Autocad
Later you can save the file if you want....