I had a 3100, when shopping I learned that Nikon created new models based on research of what generation of people were purchasing cameras. The 7000models were designed for younger people who bought up, assumed 7000 to the 7200 was an upgrade, when the main change was the lcd screen. Ask lots of questions read lots of reviews. If you have a few lenses, you will need to choose a crop sensor camera. I am ameture at best but what was important to me was speed. The 3100 is about 4 frames per second, my new Nikon D500 is 9 1/2 fps
and is super easy to use. There are tons of features you probably will not use ever.. I am giving my daughter the 3100 with a couple of kit lenses as I can't adapt to it anymore. Take your time there's a lot to learn. Love my D500