VCE UL Listed Keystone Wall Plate 2-Port, Low Profile Wall Plate for RJ45 Keystone Jack or Coupler and HDMI/Coax Modular Jack Inserts, White 10-Pack

So it's a number of things. First and foremost, you'll wanna figure out where in the house all the ethernet and coax terminate. In the IT world we call this a Main Distribution Frame (MDF), in the homeowner world we call it "that place with a bunch of random wires coming out of the ceiling (or wall)." If you're lucky, both will terminate to the same place. If not, all the Ethernet will terminate at one place, and the coax at another - very likely the coax is in a box on the side of the house that might be zip-tied shut by your ISP. There is no harm in opening this box, and you can take the time to replace the zip ties with a weatherproof lock to make things a bit prettier and more manageable. But once you know 100% you have found both ends of the Ethernet and Coax cables (individually) then use this bad boi to test them: https://a.co/d/0igGX3Ze I picked one up for a very similar project a few years ago, and it's a godsend. I recommend picking up some sort of labeling (could be anything from a dedicated label printer to just a basic Avery label sheet) to label/number the cables on both ends so you know what goes where. Regarding the faceplate: https://a.co/d/0aR0k81s this is just an example, you don't have to buy a 10-pack and can probably find an individual one at Home Depot for like $2. You'll also need some cables to go along with that tester: - Ethernet Cables: https://a.co/d/00MFzC2k - Coax Cables: https://a.co/d/02TT2WH1 Depending on where the ethernet and coax cables lead you may need a dedicated switch and splitter respectively but that's getting out of scope for your request. Hope this helps!