There are 1,000 metres in a kilometre. Therefore to convert from metres to kilometres you have to divide by 1,000. In this case you do: 3,200/1,000 = 3.2 Therefore there are 3.2km in 3,200m.
This question cannot be answered sensibly. A square kilometre is a measure of area, with dimensions [L2]. A kilometre is a measure of distance, with dimensions [L]. The two measure different things...