You have to call. They'll transfer you around a bunch of times and then take down the numbers. They'll get back to you with the info. My hubby has a few from when he was a teenager so he just went through this. They are more of a pain than anything because we can't do a package if he's going to use them and supplementing for longer than a three day trip means we have to pay for the three most expensive days.
I'm thinking maybe next time we'll do a split stay (while he's at a business meeting) so we'll get six day passes and he can use his leftover three days).