If you’re in North America, which I assume you are based on the 120v wires, then your assumption about 240v power is a bit off. Both wires can be a hot (120v) wire, 180° out of phase from each other, so they add to 240v. In this case, a neutral wire isn’t necessary to carry the current back, the other hot wire does that. A neutral wire may be used, but then there would be 4 wires.
The ground wire and the neutral wire actually connect to each other in the panel, but it’s not safe to use a ground wire in place of a neutral, so definitely don’t wire it to the neutral on the outlet.
If you are unsure of what’s going on with this set of wires, you should really call an electrician to help. Wiring a standard 120v outlet is something a homeowner can do, but identifying an old 240v cable on a dubious circuit is definitely something a qualified electrician should do.
You might have trouble getting free unrestricted library cards if you don’t live in the area that the library serves. They are usually paid for with taxes and aren’t there to serve people outside their community.
If you’re willing to pay for it, I know that the Ottawa Public Library in Canada offers membership for $90/year to people living outside Ottawa. You may find something similar at other libraries.
The Libraries and Archives of Canada will issue a card too, but you have to visit the archives in person and have a reason you are using the archives and not another library.