This is a rough estimation for the model size of a DC Motor for 1.5v-3v that you can buy a pack of 5 from amazon, by the brand Barnabas Robotics.

"Hobby DC Motor 1.5V-3V for Arduino | DC Motor with 0.1" 2mm Soldered Male Pin Wires for Breadboarding | Pack of 5"

STEP FILE vs STL FILE

So the step file format tries to preserve the solid geometry and assembly structure--use this if you want to edit the file or use it as an outline.