Where is cabin air filter on 05 Chevy pickup?

The cabin air filter on a 2005 Chevy Silverado (assuming that's the pickup you mean) is located behind the glove box. You'll likely need to remove the glove box to access it. There are many online videos showing this process for a 2005 Silverado, searching for "2005 Chevy Silverado cabin air filter replacement" on YouTube will be very helpful. The exact location and access method can vary slightly depending on the trim level, so a video specific to your truck's model is recommended.