If you think they are on your machine, I'd use the Explorer search I mentioned above. Open up "This PC", click on the Local Disk (C:), then type in *.dream in the Search box in the upper right corner. It'll probably take it a couple of minutes. It will show you the path it finds any in.
If it doesn't find them on C:, go back to "This PC" and do the same for the next drive, and so on. It should find them unless you had them stored in "My Documents" or similar under a different login on the machine.
You may need to tell DeskScapes what folder they are in after you find them. Click on "Settings" in the lower left corner of DeskScapes, then "Settings" from the popup menu that appears, then the "Add" button in the popup window, and browse to the folder.