You want something like this
To be really clear, I am not recommending this particular item. In fact this item is probably total crap since it was on the top of Amazon's sponsored list.
I used to use one of these to connect my DVD player to my network since it only had ethernet. In your case, you would plug it into your computer - make sure you get one that is compatible with WOL. Try Microcenter to find something not made by random slave labor. Anything like this from Amazon marketplace is probably either a forgery or junk unless it comes from the manufacturers store.
IMO, you should never (ever) use your personal computer over WiFi unless you really have a good understanding of internet security. I suggest you get your ISP to move your router next to your computer, and then set up a subnet if needed.
I have a WiFi receiver downstairs than connects to a switch to provide ethernet to things like my server, 3d printer etc. It is really easy to set up, just watch some YouTube videos.