"Macro" pedantically means capturing an image at greater than 1:1 on the film/sensor. As a 35mm film frame or Full-Frame widgetal sensor is 24x36mm square and slightly too small to fit a penny inside.. this means that few ever do 'true' macro photography on anything but medium and large format film. The term 'macro' has then become somewhat perverted since the advent of popular 35mm film photography, and 'macro focus lenses', which often don't put a true greater than 1:1 image on the media behind, they just have very close nearest focus distances, by engaging a pseudo extension tube behind the rear element. Which is all something of a bit of pedantry, B-U-T worth noting. If you had a camera the size of a Ford Transit, you could take a 'macro' photo of a full size person... it been done! Anything smaller and you are probably NOT doing 'Macro' photography, but close up photography, in the zone before most lenses closest focus distance.
Which begs the question; you mention getting rid of a Nikon D3200.. but keeping the lens. What lens? I have a D3200, and it shipped with the 18-55 'zoom' as it's all-round general purpose lens, and I don't think that this has a 'macro' facility. Alternatively the camera was frequently bundled with the 55-200 or 55-300 tele-zoom's, which again are not macro-focus lenses.
Close focus photography is all about, err, focus.. and particularly 'close' focus. In that, I have to say that 'my' preference when I have run into the buffers, is to forgo 'Auto-Focus'. Its a pet hate when people start harping on about 'Going Manual' and seem to believe that a) that is a mark of photographic excellence, and b) consider it solely in relation to the exposure settings, where they can find a nice neat icon that says "Manual" [Silent scream], utterly ignorant that they might also FOCUS manually.... But anyway... much has been mentioned on the matter of Electronic View Finders and back-screens, B~U~T, we are taking about 'Close Focus' and being able to focus very critically... most AF systems cant... they can be good, b~u~t, they rely on an electronic brain, a lot of trigonometry and a few algorithms to find a focus.. which even if it hits it, is only any good IF your lens can focus that close......
For close up photography, I have to say that the humble micro-sensor camera phone is pretty good.... with a diddy little sensor, the lens that gives a normal 'angle of view' tends to be pretty short. Eg the lens on my action-cam is just 4.5mm focal length, which is a fish-eye on the APS-C sensor electric picture maker.. and with such a short focal length the nearest focus diatance is virtually nothing, and the range of critical focus beyond that, where focus might be helpful is virtually nothing too! Hence the camera can be made with a factory set focus that is effectively focus free.
This is food for thought when you are talking of buying a new camera for this job.... IF you want to use a larger sensor camera, for the properties that may offer, then you have to start from a start point where you accept that its not the camera that makes much odds, but the lens. A~N~D for close focus work, you are pushing the margins of that closest focus distance almost ANY over the counter lens for any interchangeable lens camera system will have.
This begs the macro rig set up, and introducing accessories such as a reversing ring, extension tubes or bellows to shift the rear element away from the sensor and reduce that near focus limit, which is many cases begs forgoing the AF system, anyway, as they will just not work, either not able to couple through the normal lens mount contacts, or able to triangulate on a target that close. There are exceptions and work-arounds, b~u~t,
Brings us back around, to what lens, and suggests getting to grips with manual focus.
What camera is then up to you, and pretty dependent on what lens you want to use.
Mentioned I have the D32oo; and for me I see nothing wrong with, or other DSLR that as a starting point, the matter really comes down to the lens, and set up I want to use with the camera. Now if you have to forgo AF by using a reversing ring, extension tubes or bellows, what is easiest to critically focus manually? The kit lenses and many others, designed predominantly for AF, don't tend to have the easiest focus mechanism, and they tend to be rather loose, so a more dedicated lens may be more preferable. B~u~t before diving into expensive close focus 'AF' lenses, take a look at Legacy lenses, mostly from Film-Only era cameras. Loads and loads around, and not at particularly exorbitant prices. Yoou could pick up a pretty good ManFocus 50mm lens for about £50. Add reversing ring, extension tubes and or below to that, and even a lens adaptor if needed, and you are probably quids in from the go-get, and have the advantage of a much more manageable, designed for the job, 'Manual Focus', as well as being able to get well within the close focus distance of alternative AF lenses you probably cant AF with anyway!
But that's where I suggest you start, NOT with the camera, but the lens, and for close focus work, how you intend to get into those margins, via rings or tubes or bellows etc.