Your best option for .asat (Assemble SAT 3D) to .sat (3D ACIS) conversion, i.e. transformation of 3D models, is to use some of the dedicated CAD/3D modeling conversion solutions, such as CrossManager, TransMagic or similar.
Some viable alternative would be to use some middle-step conversion in one of the common exchange formats, which may help you to eventually get your models in 3D ACIS format and thus achieve asat to sat conversion.