You can calculate watt from watt-hour and hours, but you can't convert watt-hour to watt units, since watt-hour and watt units represent different quantities.
The power P in watts (W) is equal to the energy E in watt-hour (Wh), divided by the time period t in hours (h):
P(W) = E(Wh) / t(h)
watts = watt-hours / hours
W = Wh / h
What is the power consumption in watts when the energy consumption is 15 watt-hour for time duration of 3 hours?
P = 15 Wh / 3 h = 5 W