You may have noticed that when you download an Autodesk service pack, it comes in .EXE flavor only. But, when you are making a product deployment, and you want to add a service pack, it requires a .MSP file. Fortunately, you can extract the .MSP from the downloadable .EXE file using this syntax:
\\server\share\dir\C3D2015_x64_sp3.0.exe /e \\server\share\dir\C3D2015_x64_sp3.0.msp
Open a O/S command window and use the syntax above. It might take a few seconds but if successful, the MSP file will be created in the location specified.
Make note of the “/e” which is the important detail that makes this work.