The longer the focal length of the eyepiece, the greater is the overall magnification of a telescope.
The longer the distance between the objective lens and the eyepiece (or equivalently, the distance L between the image side focal point of the objective lens and the object side focal point of the eyepiece), the larger is the image one sees using a microscope.
The longer the focal length of the objective lens, the greater is the angular magnification of a compound microscope.
A nearsighted person cannot clearly see objects that are closer than 25.0 cm from his eyes.
You need a magnifying lens that has a longer focal length if you want to see a larger image on your specimen.