Thank you for the photo and I can see how the bike rack clamps would not work with a square bar, but unfortunately there is no type of adapter that is going to allow you to use your bike rack on square crossbars so the best solution if you want to use your Saab's roof rack is a new bike rack.
There are cost-effective but still high-quality options for a new rack and I recommend checking out the Yakima ForkLift Roof Mounted Bike Carrier # Y02098 which is a fit for the factory roof rack... view full answer...