Convert SLD to STP

AutoCAD slide files are some kind of presentation, a set of slides made from the program screen using the mslide command. That means you cannot produce any other CAD file from it, you have to export it from the original sources which in most cases is a .dwg file. So a direct SLD to STP conversion is very unlikely, probably impossible.

Simply put, it is impossible to convert SLD to STP directly.
Thus, there is no so-called sld to stp converter or a free online .sld to .stp converter to be found.