Conversion from Navisworks to 3MF is not supported yet :(

Navisworks is a native file of Navisworks® project review software by Autodesk.

Navisworks files come in three formats: NWD, NWF, and NWC. An NWD is a single file that contains all model geometry, environment, viewpoints, and review markups. An NWF file is a list of links to the original files. It doesn't keep model geometry and, to be opened, requires access to the original CAD files. An NWC is a cache file created from any native CAD or laser scan files, when opened in Navisworks.

The 3D Manufacturing Format (3MF) is a 3D printing format that allows design applications to send full-fidelity 3D models to a mix of other applications, platforms, services and printers. The 3MF specification allows companies to focus on innovation, rather than on basic interoperability issues, and it is engineered to avoid the problems associated with other 3D file formats.