Can't connect Bluetooth speaker

I'm using an old Dell monitor (idk what model) and a cheap roku for a tv, but neither of those have audio. When I try to connect my Bluetooth speaker, the roku doesn't even search for new devices other than remotes.

I'd go analog but I also can't seem to find to proper cable. The back of the monitor says "audio dc 12v" in front of a circular port that does not fit a normal aux cord. I can't even find a picture of something that looks like it'd fit.

Please help