* K-series Silverados: These were produced before the year 2007. If your truck's model year is 2006 or earlier, it's a K-series.
* C-series Silverados: These replaced the K-series in 2007. If your truck's model year is 2007 or later, it's a C-series.
You can usually find the model year on the driver's side dashboard, in the doorjamb, or on the vehicle's title.