All of your WindowBlind skins are saved in Public Documents/Stardock/WindowBlinds. Just copy your file folders to that location. (Note you may need to open WB Config and click on the little icon at top left and select Rebuild List)
Any way to convert the old files
Since a .wba is simply a renamed .zip, you can zip up your skins folder, change the .zip to .wba, , give it a double click and it will then self install.