To see the version of your Propertybase organization go to:
Setup | Installed Packages (see below)
In the center of the screen there is a list of all installed packages. Find Propertybase in the list. If your package says Propertybase V3 (see below) then you are on V3.x. If not you are on v2.x. Then number that is circled is the Version number of your Propertybase.