Mechanical STL Thread Repair

I have a nearly-finished mechanical part that’s ready for 3D printing, but the threaded sections are giving me trouble. Both the internal and external threads need to follow standard metric specifications so the piece mates cleanly with off-the-shelf hardware... (Budget: $30 - $250 USD, Jobs: 3D Design, 3D Modelling, 3D Printing, CAD / SolidWorks, CAD/CAM, Fusion 360, Mechanical Engineering, Solidworks)