If you are using a microscope in a biology lab, ask the lab assistant or instructor to help you learn to focus it. Be careful and handle it with both hands, putting one hand under the base and the other on the arm. There is usually a large knob for coarse adjustment and a smaller knob for fine adjustment. Use the coarse adjustment first and the smallest of the revolving lenses. When you are finished return it like you found it.
Metric system is used in science and is in common use in many European countries.
The measurements are important to be able to use. Once you get used to it, the system is simple and easy to use. It is based on 10's and easy to convert from length to weight to volume. 1 cubic centimeter. Write a paper comparing different kinds of microscopes and their uses.