Very difficult to see with the black theme but, I think you might have made the plugin folder and left a "dot" at the end.
Ofnuts makes good packages for his plugins and all you need to do is open the zip file and copy the plugin folder to the correct location. C:\Users\"yourname"\AppData\Roaming\GIMP\3.0\plug-ins and you get the plugin files + a "how-to" EDIT not the best image but that is the zip file opened not put the zip in plug-ins
Ofnuts makes good packages for his plugins and all you need to do is open the zip file and copy the plugin folder to the correct location. C:\Users\"yourname"\AppData\Roaming\GIMP\3.0\plug-ins and you get the plugin files + a "how-to" EDIT not the best image but that is the zip file opened not put the zip in plug-ins