To be certain, you should:
1. Check your owner's manual: This is the most reliable source of information. The manual will show you exactly where the jack and other tools are stored in your specific model year.
2. Look under the rear of the truck bed: Carefully examine the area under the carpeting and any storage trays. The compartment is usually fairly obvious once you locate it.
Don't forget to also check for the lug wrench and other tools, usually stored with the jack.