Instructional world vs Real World
For simplicity and SOP flying clubs normally use a standard power setting for the teaching of the normal flying. This setting is used regardless of conditions to simplify things for the student and in the early stages of flying this practice is no bad thing but sticking to " flying club standard " is not good post PPL.
A long look in the flight manual will give you a range of power settings and the RPM to set to get the % power setting for differing altitudes.
Along with this are graphs to show the fuel consumption and speed you can expect from the settings.
This is not something that can be covered by posts on an Internet forum but I hope that mine and the very useful posts above will point you in the right direction to find the information in the flight manual that you need.