How to make Firefox recognize an existing profile

I'm using Firefox in Windows. I lost all of my bookmarks... never mind how, I think I can prevent it from happening again... and I'm trying to figure out whether there is a way to recover them. Looking in the profile folder, I see three profiles. One is listed on the about:profiles page, and is identified as the default. The other two aren't listed there at all. I need to select each of those other two and see whether my bookmarks can be recovered from them. But how. The about:profiles page has a button for creating a new profile, but not for adding an existing profile to the page. Either it's listed there or it's not. It seems to me that I could create a new profile and make it the default folder, then quit Firefox and replace it with a copy of one of the profiles I want to investigate. However, I lost my bookmarks by doing something similar to that, so I'm wary of doing it again. Can someone explain what is happening here--why there are three profiles in the default profile's folder but only one list listed, and why there's apparently no provision for making Firefox list the others?