First of all there is no
folder called gta3, there is only a file that's called
gta3, and its file type is
.img in case you're wondering. You may have placed it somewhere else by mistake, so the easiest way to find the location of the file, if you haven't found it by the suggestion of the guy above me, is to use the search bar. And I suggest you to search inside the search bar of the GTA SA folder instead of the models folder in case it has been placed in another location.
Like this:
Just go to the GTA SA folder itself, and type in the search bar
gta3, the search bar is located in the top right corner.
After you've done so, you should see the file. Then, right click on it and click on "Open file location" to go its location.
Now place the file back in the "models" folder.
