The correct answer is - at the low left part of the map.
The maps have multiple elements, and one of those elements is the scale. The scale can be found on the lower part on the map, on the left side. It serves to give us the information about the distance on the map, in comparison to the actual distance in reality. This information can be shown either as unit to unit, or as measurement to measurement.
Example:
1:100,000
This means that one unit on the map, will be equal to 100,000 same units in actual distance. So 1 cm on the map, will be 100,000 cm in real life.