If the electrical outlets in your home have three prongs, it’s safe to say that the wiring connected to it has been appropriately grounded. Knob and tube wiring does not feature a third plug-in located just below the other two, and thus does not adequately protect from electrical shock if a wire comes loose.
If you’re trying to figure out what type of wiring your property has overall, however, simply checking your outlets for two or three plugs will not be enough. Since other electrical systems, such as sheathed duplex electrical wiring, also use two-pronged outlets, you’ll need to be more in-depth with your research before coming to a final diagnosis.
Unfortunately, if you’re hoping to ground an existing k&t system you will be sorely disappointed. In the interest of staying up to code—not to mention ensuring your home is properly, and safely, wired top-to-bottom—you’ll have to rewire the whole property.