The dissertations are now in Information Store B, on your left hand side if you come up the stairs from Information Store A.
You can search for dissertations by going to Blackboard > Information Store Catalogue > Advanced > change the "Medium" to "Dissertation".
Alternatively, simply browse the dissertations. They are in the same order as your books, so if you usually find your books on the shelves at 370, look at dissertations numbered 370.
And, as always, just ask if you need help.