How To Change Format Of Player model?

Okay, I am using Revolt Servers Control Panel and I got the Skins extracted from a GMA File and have the .lua file. So, I go to
garrysmod>addons>Pointshop by _ Undefined>lua>items>playermodels> and add the Player models “.lua” file and save it. But according to a friend of mine, he said “they all are in like default addon format, so you’ll need to change them.”
But, I have no idea what Format is or how to change it? Sorry, I’m new to all of this.

models are .mdl files, not .lua files.

The files you had where simply adding the player models to be spawned via the spawnmenu. That won’t add it to the pointshop. You need to modify the current files to reflect the pointshop format which will then add them.