What you need is the consumed land impact. There a couple of ways to get it.
The "About land" floater (ALT L) gives you the "Primitives on parcel" usage in its "Objects" tab (sadly, when not the owner of the parcel, you can not list the number of objects per owner). You could check that number before and after you rezzed your stuff (on the condition no one else is (un)rezzing other stuff on that parcel at the same time, of course).
Another way is to use the "Edit" floater (CTRL 3) and lasso-select (left click and drag mouse to surround all your objects with the rectangle selection outline) all your objects at once to get the total LI.
You will first have to make sure "Tools" -> "Select only my objects" and "Selected by surrounding" are checked, that "Tools" -> "Show hidden selection" is un-checked (to avoid too much of a fps slow down when many objects are selected at once), and that the "Limit maximum selection distance to:" check box is not ticked in the "Preferences" floater, "Input & camera" tab, "Input controls" sub-tab. The LI is then displayed (in parenthesis) in the Edit floater, like so: