Galileo made his milestone observations with telescopes that never magnified more than 30x. And the 60mm refractor, the most common one purchased by beginners, offers far better image quality or resolution than Galileo's telescope had. Well, certainly not the 200x, 300x, or 500x the manufacturers of many 60mm refractors promise. There is an upper limit to how much magnification a telescope will deliver. For a 60mm refractor, that's 2.4x20, or about 50x.
High power provides better detail of the moon and planets.
It's a simple math problem. Somewhere on the tube of your main scope is a label that describes the aperture and focal length of the objective lens, expressed in millimeters. It's the latter number, the focal length of the objective, that we want. Now look closely at the eyepiece. You'll see the eyepiece focal length in millimeters.