How do you convert 28cm/s - km/hr^2?
One way is to go to www.google. com and type in 28 centimters per second to kilometers per hour. (I'm sure you meant hour and not hours^2.)
The other way is to do with conversion factors.
There are 100 cm in a meter.
There are 1000 meters in a km.
There are 60 sec in a minute.
There are 60 minutes in an hour.
28 cm/s x (1 m/100 cm) x (1 km/1000 m) x (60 sec/1 min) x (60 min/1 hour
Post your work if you get stuck.