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

Powermill is a 3D Computer-aided manufacturing app developed by Autodesk Inc. It runs on Microsoft Windows and is used in many different engineering industries to determine optimal toolpaths to reduce time and manufacturing costs.

Powermill rapidly creates toolpaths on large, complex parts, works with surfaces, solids and STL meshes. It uses efficient roughing strategies and can create gouge and collision free toolpaths, which can be edited and optimized. The software obtains comprehensive range of finishing toolpaths, user-defined macros and templates for automated CAM, extensive library of tool types for use with 3- and 5-axis milling, and specialist tools for demanding industries and applications.

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.