Conversion from Nastran to Parasolid 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

Parasolid file format is native for Parasolid geometrical kernel. Today it is widely used in a range of applications, including SolidWorks, SolidEdge, NX, Microstation, Ansys, Abaqus and others. Parasolid has two primary file extensions: .x_t, which is text based, and .x_b – binary-based format. Parasolid is also used to provide precise geometrical definitions of parts in JT files (as XT B-Rep data segments).

CAD Exchanger can read files compliant with the entire range of Parasolid file format (schema) starting from v0.15 and up to version 32 (as of time of writing this page). Likewise, CAD Exchanger writes file compliant with all Parasolid schemas.