Arrange the following lengths in their increasing magnitude:

1 meter, 1 centimeter, 1 kilometer, 1 millimeter.

1 kilometer (km) = 1000 meter (m)

1 meter (m) = 100 centimeter (cm)

1 centimeter (cm) = 10 millimeter (mm)

Hence, the ascending order of given unit is as follows:

1 millimeter < 1 centimeter < 1 meter < 1 kilometer.