I cannot find one
The 2006 GMC Sierra 3500 SLE with the LBZ 6.6 Duramax does not have a cabin filter.
they do not have a cabin air filter
How to Replace a Cabin Air Filter on a 2006 GMC
The cabin air filter on a 2005 GMC Sierra is changed by removing the cover under the glove compartment and opening the filter housing. The old filter is then removed and a new filter put in its place.
There is no cabin air filter on the 2006 year model of the GMC Yukons and Denalis.
Purchase a Purolator cabin filter for your truck, it comes with complete instructions.
Under the dash on the passenger side.
Remove the glove box door. The cabin filter is in a holder on the left side of the heater core.
In a 2010 GMC Sierra, the cabin air filter is located behind the glove compartment. To access it, you typically need to open the glove compartment, remove any contents, and then unclip or lower the compartment to reveal the filter housing. The filter can then be removed and replaced as needed.
http://www.youtube.com/watch?v=bml8dletNbk hope this helps
The cabin air filters are located in the heater box above the lower panel, mounted below the glove box.drop the plastic panel, 3-7mm screws, then you will see a black access panel, with 1 screw holding it up. the 2 filters are located there. Sorry, I misread the question and read it as 2000 GMC Sierra. Your 2008 GMC Sierra doe not have a cabin filter.
it doesn't have one