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.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.