Looking through a microscope the field of vision is 2 millimeters across. How many 2 micrometer cells could fit end to end across the 2mm field? I know there is a ratio formula that I just need to plug the numbers in, but I can't remember how.

1 millimeter = 1/1000 of a meter

1 micrometer = 1/1000000 of a meter

Thus, 1 micrometer = 1/1000 of a millimeter