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

A Brep file is a 3D model stored in the boundary representation (also known as B-rep). The Brep format is a part of Open CASCADE Technology (OCCT).

The Brep structure is made up of two major components:

• topological components such as faces, vertices, and edges;
• links between components such as surfaces, points, and curves.

It comprises three-dimensional data such as vertices, edges, wires, faces, shells, solids, compounds, edge and face triangulations, polylines on triangulations, space location, and orientation.

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.