Using the debug tools, you can shift+click in a building and chose the option Dump to .QB
That will create an *.qb file at the game folder. The name of the file will be the same name of the building. The screen below (from my game folder) shows the build named lala got exported as lala.qb, while the building shown in the previous screenshot had no name, so it got its number, as 1.qb
And here the file imported into MagicaVoxel (one of many model editors you can use)
Notice that only blocks are imported, the items all all ignored.