Where can you find a diagram of the parts pistol?

A diagram of the parts of a pistol can be found in the owner's manual that comes with the pistol when purchased.

Another way to find these diagrams is through a simple Google search or browsing websites like gunpartscorp.com, midwayusa.com, brownells.com

Additionally, many manufacturers' websites include interactive parts diagrams with detailed information about each component. Finally, exploded view diagrams for firearms can be found in gunsmithing manuals and reference books on firearm assembly and disassembly.