Strata Design 3D CX can import several formats: STL, DXF (R12), U3D, OBJ, Collada, and VRML2 (97). STL may be your best option. If you can export one of these formats then you should be able to import your data into Design 3D CX.
If not, then you could use another program that can import the file, then export it to one of Strata's supported import formats.
Another option many Strata users utilize is a third party conversion utility - Okino Polytrans on Windows is one option. On the Mac, several of our users recommend ViaCad, which costs about $100.