From the airport to The Pearl it would be some 15-20 Kms.

There are no shopping malls there; instead several High End stores located all over the "complex".

If you have a car check the link to see the way and get alternate routes

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Doha,+Ad+Daw...

If you don't have a car take a taxi and ask them to drop you in The Pearl.

Regards!!