There is a chance it’s “outside” in some sort of deep box but that seems unlikely unless you are in the south.
You need a plumber unfortunately and if you really don’t have one it might be a grand or more. Schedule with water company to turn it off at the street, cut, add a good modern shutoff in a useful location (which might require changing layout) and so on.
Good luck, but I would not do it myself based on the comments so far. Just fyi.