When replacing brake pads, do you reuse the shims that are currently on the truck or do you replace them?

This picture is what you would get in a shim kit. If anyone can help me with the terminology for what the red dots and blue dots designate, that would make for easy reference.
Anyway, I'm in the process of installing powerstop rotors and pads at the rear and I have a question that maybe some of you can help me with. The powerstop pads have a thin piece of metal that is adhered to the back of the brake pad (is this a shim?) If i were to order the above shim kit, would i install the pad in this order: red dot, blue dot, pad, rotor, pad, blue dot, red dot. On the current shims that came off the truck, the part designated by the red and blue dots were almost fused together. I separated them and in the process, damaged one of the blue dot parts. I'm hoping this makes sense. I'm trying to dumb this down so others like me (i am assuming there are others like me), can make sense of this and try their hand at wrenching on their own trucks.

This picture is what you would get in a shim kit. If anyone can help me with the terminology for what the red dots and blue dots designate, that would make for easy reference.
Anyway, I'm in the process of installing powerstop rotors and pads at the rear and I have a question that maybe some of you can help me with. The powerstop pads have a thin piece of metal that is adhered to the back of the brake pad (is this a shim?) If i were to order the above shim kit, would i install the pad in this order: red dot, blue dot, pad, rotor, pad, blue dot, red dot. On the current shims that came off the truck, the part designated by the red and blue dots were almost fused together. I separated them and in the process, damaged one of the blue dot parts. I'm hoping this makes sense. I'm trying to dumb this down so others like me (i am assuming there are others like me), can make sense of this and try their hand at wrenching on their own trucks.