Change coil pack 2002 Chevrolet trailblazer what is cylinder number 1?

On a 2002 Chevrolet Trailblazer, cylinder #1 is located at the front of the engine, on the passenger side. To be absolutely certain, check your Trailblazer's owner's manual; it will have a diagram showing the firing order and cylinder location. The coil packs are usually arranged in the same order as the firing order.