How to save assembled 3 parts as a whole stl for printing

Hi

When I save my assembly project which has 3 parts as a .stl file for printing, solidworks saves it as 3 parts.

Is there a way to save my 3 parts in assembly as a whole .stl all together for a solid print..

Im using SW 2017

thank you for any help.. TOM

SolidworksAssemblies