Good evening, Yes the adaptor wil work very well. You have to set the camera manually to shoot. Please note the camera must first be set to manual with the original lens attached,it's impossible to access the shooting menu without this lens. Exposure will be trial and error but I think you will find the results worthwhile especially I mono, Regards 

Nope, it’s to adapt to the smaller Nikon 1 (CX) mount of the 1 series camera, not the F mount (your D3100) on crop and full frame Nikon’s. 

You can attach any Nikon F mount lens to it but there is no electrical contact so an AF-S lens will be manual focus only. Also there will be no metering so exposure will be trial and error. The aperture will also be stuck to its smallest setting, likely f/22 so the screen will be dark. If you have a "D" lens with an aperture ring then you can set it at it's widest setting to focus and then stop down if necessary. Similarly boosting the ISO to aid focus may work. I have a 90mm macro lens with an aperture ring and I set it to f/2.8 to focus and then rotate the ring back to my desired aperture if necessary. One workaround to help with the aperture would be to use either tape to hold open the aperture before mounting the lens or blue tack. Even with all the added problems to use an F mount lens with this it is still cheap and kind of fun. 

As the adapter does not have the contacts then your autofocus cannot work.