The distance of 250 meters is equal to 0.25 kilometers. One kilometer (K) is equal to 1000 meters (M), so the formula M / 1000 = K is used to convert meters to kilometers. Alternatively, one could use M * 0.001 = K to covert the numbers as well.
Meters and kilometers are part of the metric system of measurement. Similar metric system concepts date back to the 16th and 17th centuries. In 1799, the first practical idea for the metric system came to fruition, and the decimal system at the time was based on the meter and the kilogram. The meter is a unit of length, while the kilogram is a unit of mass, and the liter is a unit of volume.