Generally, there are two types of Arca-style bracket/plates you use with DSLRs.
The first is a plate that simply attaches to the bottom of the camera, typically also allowing access to the battery compartment (above is a plate for the D850). You can find many different plates for most Nikon DSLRs at this site's exclusive advertiser, B&H. I tend to use Kirk or Really Right Stuff plates with my cameras, though I have several other brands and even some generic ones. In general, I recommend that you use a plate designed for your specific camera, as they'll have a bar that helps keep it aligned and not twisting on the bottom of the body (as you can see at the back of the above photo).
The second is called an L-bracket, which allows the camera to be used in both horizontal and vertical orientation (Really Right Stuff bracket shown above). You might notice the cutout on the vertical plate. That's because a good L-bracket allows you to still use the cable connectors on that non-grip side of the camera. Some L-brackets get quite elaborate about this, allowing the vertical portion to be removed, or to be moved further from the camera. This site's exclusive advertiser, B&H, also sells L-brackets for most cameras.
Note that if you use one of the MB-D## vertical grips with your camera, you'll need a different plate or L-bracket for that.
Video shooters will tend to prefer a "cage" to a plate or bracket. See this page for cages.
