A:
The D3100 has a standard Nikon F mount with AF contacts. The F mount is the same mount Nikon has used for ages. All Nikon /.Nikkor lens fit this mount. There are a few older lens that may not fit due to manual connections, but those are highly specialized and few and far between.
Since you have a Pentax Lens with a Pentax K mount, the answer is No, you cannot use those lens on any Nikon camera.