What lens adapter should I use?

I purchased my first DSLR few days back Nikon D5100 with the kit lens. My dad have his old SLR, which he purchased approximately 30 years back.

Camera: Asahi Pentax K1000

Lens: Lens: SMC Pentax-M 1:2 50MM
Tefnon H/D-MC zoom 1:3.5~4.8 F=35~80MM Macro

My question is how can I use these lenses in my Nikon D5100?

Just look for any k mount adapter for your camera. There's a cheap one on amazon and a couple on ebay.

Also the Asahi Pentax K1000 is an amazing camera, I just gave one away as a birthday gift two days ago. If you learn to use the K1000 you can set your D5100 to manual mode and you'll be all ready to shoot like someone who actually knows how to use a camera.

Now of course, I should note that obviously you'll have to manually focus the lens.

These lenses would fit a Pentax DSLR without an adapter and allow metering - neither of which is possible on your D5100.

You could get a k-mount adapter, but I doubt it's worth the hassle.

As far as i know there's no adapter available to mount Pentax K mount lenses on a Nikon F mount camera. Those things just don't fit together.

Any use of an adapter would come with serious drawbacks, such as loss of metering and autofocus. They're not worth it except for truly outstanding legacy lenses (e.g.old Zeiss ones).
Your 50mm/1.2 lens is interesting, but since the use of an adapter (if there were such a thing for this combination) also might cost a stop worth or so of light, that'd render the strong point of that lens moot.

Perhaps you can return the D5100 and buy a Pentax K30 or Kr instead - if you really want to use these lenses. The 35-80mm one is unremarkable.

Edit:
Two thumbs down - anyone care to explain where i'm mistaken?

There are adapters (link) but you will lose autofocus and metering. Does you Dad have an old exposure meter?
You should buy Nikon or Tamron/Sigma lenses that work on your D5100.

Suggest a f1.8 50mm Standard lens for good quality portraiture and a 70-300 telephoto.

Easy. Sell the Pentax lenses then use the money to buy a Nikon lens.

or

Sell the D5100 then buy a Pentax dSLR.