The AWD stopped working. Only the front wheels drive. on 2006 Volvo XC70

My mechanic said there is a connector between the front wheels and the back wheels that needs to be replaced. About how much does that cost?

Asked by for the 2006 Volvo XC70
You can try the estimator here.
On this website? Where?
At the top of this page where it says ESTIMATOR!
How am I supposed to do that if I don't know what the part(s) are called?
Maybe you should have written it down! I am pretty sure the mechanic said something about a DRIVESHAFT. Another name for it is the PROPELLER shaft. No price from your mechanic?