Each page you open up in the web prototype has a unique link in the address bar, so you can copy that and give to a dev, without making them search for it in grid view.
If you want to generate a new unique link for only that artboard in Xd, you have to first duplicate it and remove all its links to other artboards. Then you have to select the artboard and click on the little share icon that pops above its name while in the Design tab:

This creates a separate flow, containing only this artboard, which you can generate links for.
The reason I'm telling you to duplicate it and strip the links is because if you don't, and it's linked to other artboards, they will be included in that second flow, and their links will all be messed up, which you don't want.