D-Link Camera Feed - Which URL to use?

You need the camera's IP address. It's going to be something like 192.168.0.4. Then you can quickly make it into the URL you need such as: "http://192.168.0.4/suffix" where "suffix" is one of the "RSTP URL" strings from the screen you posted or just "mjpeg.cgi" for default video or just "image.jpg" to get a still frame. There are a couple subtleties. If you're not on the same local network, you'll need to use port forwarding or some such to make the port visible. And if you haven't opened it up, you may need to supply credentials. One way to do that is to make the URL look like "http://username:password@192.168.0.4/suffix" - but that won't work with some browsers, notably Chrome.