Conversion from Intergraph Smart 3D to Unigraphics is not supported yet :(

Intergraph Smart 3D, the most advanced plant design software offered in two decades, is Intergraph’s next generation, data-centric, rule-driven solution for streamlining engineering design processes while preserving existing data and making it more usable/re-usable. A fundamental component of Intergraph’s SmartPlant Enterprise, Smart 3D is a complementary, full-suite solution that provides all the capabilities needed to design a plant, and then keep it as built throughout its life cycle.

Unigraphics is a former name for Siemens NX, an advanced CAD/CAM/CAE software application suite. However, veterans are still using the Unigraphics name.

In 2002, the new version of Siemens Unigraphics, merged with I-DEAS software, was released and called NX, which means "Next Generation". In fact, it was the last version of the software released under the Unigraphics name. All further releases became known as NX. So the addition of I-DEAS functionality to the core code of the Unigraphics has become the basis of the existing NX product line.

Siemens NX / Unigraphics use a .prt extension, which contains 3D CAD parts.