The software is not available for installation. You can still obtain it through the its application page at Software Informer, but there will be no way to register it because it redirects to a page with a different product. It's impossible to say if it support STL extension as output format if the software is not available for installation. If you have it installed, go to File > Save as to check the supported output files.
To obtain an activation username and password for the old software, contact the developers: