We have found 3 software records in our database eligible for .dwfx to .stp file format conversion.
Everything points to the fact that the only way to reliably export .dwfx files (Autodesk Design Web Format) to other appropriate formats, including possible dwfx to stp conversion, is to use one of the Autodesk's own programs, such as Inventor or AutoCAD.
Alas, we do not have information about any 3rd party app that would support export of .dwfx files, so this looks like your only option how to convert dwfx to stp.
Updated: January 10, 2023
DWFX
Files with dwfx extension are pretty much always CAD files in Autodesk Design Web Format. These are used by various Autodesk applications for distribution and communication of rich design data to anyone who needs to view, review, or print design files.
STP
Files with stp extension can be typically found as CAD format in the STEP, a ISO standard for the computer-interpretable representation and exchange of industrial product data.