To find it:
1. Locate the underhood fuse block. It's usually a black box near the battery.
2. Open the fuse block cover. There should be a diagram on the inside of the cover showing the fuse layout and what each fuse controls.
3. Refer to the diagram to find the fuse for the power outlet. The diagram will usually show the amperage rating of the fuse as well.
If you can't find it using the diagram, consult your owner's manual. It will have a complete fuse box diagram with locations and amperage ratings for all fuses and relays. You can also search online for a fuse box diagram specific to your 2006 Silverado's trim level and options.