Your vehicle is equipped with a "Driver Information Center" in the center of the dashboard that gives you a lot of options and displays. These displays (usually in the INFO category) can tell you everything from tire pressures to average fuel economy. As part of these displays, there is an indicator that shows you "V8" (or "V6" on EcoTec V6 models) and V4 (or "V3" on EcoTec V6 models).

To access this information, you use the steering wheel controls on the right side or the button on the dash for the Driver Information to scroll through the information in the screen in the center of the dash under the gauges.

On the pre-2014 models, it is usually a single button on the dash to the right of the steering wheel and single presses will scroll to the next information screen.

On 2014+ models equipped with the LCD screen, you use the steering wheel buttons to scroll through the options in the INFO category.

Below is an example from a 2014 Silverado ... most 2014/2015 models are similar: