Would this lens fit this camera?

My current camera, the Nikon D 31oo, came with a 18-55mm f/3.5-5.6 AF-S DX VR Nikkor Zoom Lens

my boyfriend is thinking of ordering the Sony NEX-5R/B 16.1 MP Compact Interchangeable Lens Digital Camera with 3-Inch LCD (body only)

would my lens fit that camera?

No! Sorry with digital, only Sony fits Sony, maybe some older Minolta film cameras, Canon only fits Canon due to the stabilization feature built into each lens. The same is true of Nikon. Pentax has the stabilization built into the camera body, therefore older Pentax lens (even from the "film" days) will fit the Pentax DSLR's.

No.

Lens mounts are different with each camera brand. You can't interchange. There may be some adapter available but the loss of optical quality won't make it worthy.

With an adapter it could be used. However, it will be a nuisance with no autofocus or metering. An attractive feature of mirrorless cameras is compactness. The SLR lens is more bulky than the dedicated mirrorless lens, and adding the adapter makes it even more bulky. Buyiing the mirrorless camera as body-only is only smart if one already has the lenses for it. He will be much happier with that camera buying it with its kit lens.

No. All camera manufacturers use a proprietary lens mount so there's no compatibility between brands.

Nikon uses the "F" lens mount which has been in existence since 1959.

The Sony NEX cameras use the "E" lens mount which was introduced in 2010.

Well no you can't do it directly and i also tried to find an adapter but came up with nothing i think you need to stop wasting your time on this