Pulley STL-to-STEP Conversion Fix

I have two pulley models that are currently only available as STL meshes. I need each one converted into a clean, fully-solid STEP file that imports into any mainstream CAD package without errors. During the conversion please check the geometry carefully: remove mesh artifacts, close any tiny gaps, heal non-manifold edges, and ensure the bores, grooves, and overall dimensions remain true to the original shape.

NOTE:Dimensions are in MM.

What I expect back:
• Two separate STEP files, each representing a single watertight solid body
• Geometry that passes a “solid-check” in software such as SolidWorks, Fusion 360, or Creo
• No faceted surfaces—faces should be properly parametrised so the parts can be edited further if needed

If you typically work in tools like SolidWorks, Fusion 360, SpaceClaim, or Rhino with an add-on such as Power Surfacing, that will fit this task perfectly. Let me know your preferred approach and a realistic turnaround time, and I’ll share the STL files right away.