In general, ProfilmOnline is not suitable for displaying and analyzing the type of 3D models that are described by .stl files - that’s why we recommend Sketchfab for that purpose. ProfilmOnline is designed for images representing what you see when you look at the surface of an object. If you can represent your data as a regular grid of height values that are evenly spaced in both x and y directions, then you can upload it. See this post for details.