Just for fun…
Let’s say that instead of using the asteroid belt, we instead colonized a binary star system whose components were two 80-solar-mass stars. We then mine all the stellar material through star lifting, transmute it into carbon and other building materials via fusion, and use that to construct space habitats.
160 solar mass are about 3.2 x 1032 kg. That would make 2.1 x 1020 habitats, suitable for about 25 trillion trillion human beings to live in. Of course we might want to set aside some solar material to still power (via fusion) our “habitat galaxy” otherwise it might get quite dark and cold, but that would only likely be a few percent of the original stars’ masses.
I first calculated this scenario several years ago and it still boggles my mind just how much stuff is out there.