Firstly, please use code tags .
Secondly, variable/reference name should start with a lowercase letter, otherwise it is assumed you are trying to reference a class itself, which may be the reason why this line is not working:
Rocket = GameObject.Find("Active_missile").gameObject;
But if that isn’t the case, then make sure a GameObject named “Active_missile” (spelled exactly like that) exists in the scene when this script runs.