To find the correct amount, you must consult your owner's manual or a repair manual specific to your Chevy 1500's year and model. The information will be in the fluids section, often with a diagram showing the transfer case location and capacity.
Alternatively, you can search online using your truck's year, model, and transfer case type (this information is usually found on a tag on the transfer case itself). This will likely lead you to forums or repair sites with the correct information.
Never rely on a generic answer. Using the wrong amount of fluid can damage your transfer case.