Sweet! ThanksThere is a free Online 3D File Converter:
http://www.swiftconverter.com/convert_3d
Yeah, it turned out that this one never converted my file. It just displayed a message saying I was 5th in line and "this might take a while". After 4 hours I just shut the window.I'm weary of free or online converters and never upload sensitive, confidential, or proprietary information (including information in the form of a 3d model). Some may be nefarious. I'm not saying this one - I'm just saying to judge your risk.
Not yet as STL files are all I need for now, saw above that could be an option, just wondered if 3mf would become a native export format.Have you already tried Alibre OBJ Export?