Ahydrogen atom has a diameter of about 10 nm. express this diameter in meters. express this diameter in millimeters. express this diameter in micrometers.

1.x 10^-8 m (meter)
1 x 10^-5 mm (milimeter)
1 x 10^-2 μm (micrometer)

In this case, you are told to express diameter of nanometer(nm) in meter, milimeters and micrometer, which was a bigger unit. When a scientist refers to a bigger unit they use 10^-X to make easier counting. Nano meter is 10^-9 meter, or 10^-6 milimeter, or 10^-3 micrometer.

In case of micrometer 10x 10^-3 would equal to 1 x 10^-2