As mentioned by @osullic, Nikon G lenses don't have aperture ring. Aperture is actuated by the body via a lever in the rear mount barrel. Older D lenses have both focus and aperture ring on the lens barrel.
Concerning adaptation, you need to find a Nikon G (or Ai(G)) to M4/3 adapter. With this of adapter, you will be able to mount both G and D lenses. Note that the additional ring dial on the adapter will remain useless for D lenses.
Using an adapter means that you won't be able to use any electronic lens command. Aperture and focus will be driven manually. To get more precise control over focus, you may want to activate focus peaking in your camera.
As per brand, I would recommend K&F Concept adapters. They are cheap and well built (CNC machined).
Future-proofing your system :
With the adapter, you will have a 70mm and a 100mm equivalent on your M4/3. This is quite telephoto and may not be as multi-purpose as a 50mm equivalent you have on APS-C and FF.
And if, you additionally find the adapted lenses a bit cumbersome on the GH3 (despite its good grip).
You might want to lurk on the excellent Lumix 20mm f1.7 for a more multi-purpose lens for your M4/3. A bit wider than the 50mm equivalent, try it before buying to see if you like it. People are often polarized on this kind of focal length: 40mm equiv. But its output is praised all over the internet.