Where are the fuel injectors on the 2002 Trailblazer and how many are there?

The fuel injectors are located on the fuel rail by the Intake Manifold.

If you have a 6 Cylinder than you have 6 if you have a V8 you have 8.

Try to follow your fuel line and it will lead to the fuel rail and you will see your injectors are perpendicular to the fuel rail.