equipment recommendation - How do I use a Macro Lens for Jewelry Photography?

I've been looking to upgrade the camera I use at my job. Thinking of getting the Sony a6000. We list things on ebay to sell, and quite frankly I just don't like the lightbox, nor the camera we currently have.

We're using a Nikon D3100, and I forgot the name of the Macro Lens.

Basically, I want to have my own personal camera, that's better than the D3100, but one I can use at the job as well for when we photograph our jewelry.

I do mainly macro photography in the lightbox, and I'm working on my own setup with better lighting and other things to improve our photos. I just ordered an external flash for the D3100 so I can over expose the background to get a nice white one with the pics when I finish my own setup as well, but I digress lol.

I need suggestions for what I should look for in a good macro lens to use when I photograph jewelry. I mainly work with rings, but I also do pictures of pendants/charms, necklaces, bracelets, watches, and other related items too.

Right now I'm considering the SEL30M35. But I haven't bought anything yet (Including the new camera)

To get a better idea of the type of photos that I'm producing with the Nikon, you can check these out: (I don't have the stats for the Aperture, Shutter Speed, ISO, etc)

You can see that when you're 100% zoomed in, things aren't that detailed. Don't get me wrong I've had some nice shots. But that ugly grey background usually says otherwise. I use different backdrops in the cases when the background looks too ugly. I take all my pics handheld, Manual Mode, the focusing is Auto Manual (focuses when I hold the shutter release halfway) and when I'm at the lightbox the rings are only about 5 - 8 inches away, unless I bring them closer to get detailed diamond shots. (Which, I might add, aren't too good.)

I want to get some photos as close to these as possible:

I'm still an amateur, and I'm still learning, but I really want to take better photos. I'd love for them to be sharp and really detailed on most parts of the subject. That and seeing the photos on an LCD screen with the a6000 before actually snapping them to have a look would save me a lot of time.

Merging some of the macro shots to get everything in focus (I think its called focus stacking), and to use focus peaking on the new camera would probably help me a lot more as well. That and a lot better lighting than the lightbox gives off.

Heck, maybe these photos are actually good and I'm just too picky lol, idk.

Anyway, what do you guys think? Would the SEL30M35 macro lens be a good lens for my needs with the jewelry photography I'm trying to do? I understand some lenses aren't compatible with the auto focus or something like that on the a6000 (maybe the E-mount?). How can I be sure they're compatible? Or if I need an adapter, can you suggest one as well?