1. Do not use the root folder, you can use it but you need to be root to put files there. Use your Gimp user profile files which you will find in ~/.config/GIMP/2.10/ Note this is a hidden folder (starts with a dot) toggle hidden visibility in your file browser (it will be there somewhere)
(Edit: Unless you are using a flatpak Gimp in which case look in ~/.var/app/org.gimp.GIMP/config/GIMP/2.10/plug-ins)
2. Then a possibility, it is a Photoshop pattern, they have the same .pat suffix as a Gimp pattern but very different type of file.
If it is then you need a PS pattern loader. The one I use is attached. Looks like Zorin is based on 'buntu so it should work. Unzip it, put the ps-pat-load_64 plugin in your user plug-ins directory ~/.config/GIMP/2.10/plug-ins/ It should already be executable but check anyway.
A PS pattern file is usually multi-layers, Open it as you would any other graphic file. example in kubuntu 18.04
https://i.imgur.com/qMyC3K9.mp4
Use your favourite layers-to-images script to separate into individual images. Gimp will use jpegs and png's as pattern files as well as gimp .pat Put in your patterns folder ~/.config/GIMP/2.10/patterns
3. Of course, if it is a regular Gimp pattern file, then just put it in ~/.config/GIMP/2.10/patterns When you start up Gimp the pattern will be in the patterns dock under its name.