Editing Custom Weapon models

Hi there,
Since a short period i hae been editing weapon models, because it keeps be busy :)
Now iam actually haVing my first attempt on creating a selfmade 3d model in Blender
And this is how it turned out Screenshot_3.png

Iam going to put some lengthwise fires at the exact same places once im done with it.
Now i dont know if the .smd, or the .ski is the actual model for this weapon
Or what both of these (.smd .ski) files do/are. Like how do i make the model bigger/smaller etc

i would appreciate some help!
TYVM :)

Attached Images

• Screenshot_3.png (154.2 KB)