Conversion from Nastran to SLDASM is not supported yet :(

MSC Nastran is a multidisciplinary structural analysis application used by engineers to perform static, dynamic, and thermal analysis across the linear and nonlinear domains, complemented with automated structural optimization and award winning embedded fatigue analysis technologies, all enabled by high performance computing.

Engineers use MSC Nastran to ensure structural systems have the necessary strength, stiffness, and life to preclude failure (excess stresses, resonance, buckling, or detrimental deformations) that may compromise structural function and safety. MSC Nastran is also used to improve the economy and passenger comfort of structural designs

SLDASM is a SOLIDWORKS Assembly File. It refers to a SOLIDWORKS 3D assembly, which consists of several SOLIDWORKS part files (SLDPRT). An assembly file itself may contain some children SLDASM files, as well as some SLDPRT part files.

SLDASM are proprietary files with closed specifications. Nevertheless, some APIs (like CAD Exchanger SDK) provide the facility to read and convert them to other formats.

Software applications like Autodesk Fusion 360, Okino PolyTrans, and AMADA SheetWorks can import and render SLDASM files created with SOLIDWORKS.