m/s to km/h is easy. There are 1000 m/km and 3600 s/h (60 m/h times 60 s/m = 3600 s/h).
So 43 m/s= 43 m/s * 3600 s/h= 122400 m/h . Then 122400 m/h* 1/1000 km/m= 122.4 km/h. (Notice that in order to "cancel" the "m"s and get "km" in the numerator, I had to invert 1000 m/km to 1/1000 km/m.)
miles per hour is harder to convert since it is not a simple number: there are approximately 1.61 miles/ km or 1/1.61= .621 km/mile. 60 miles/h*.621 km/mile= 37.3 km.