You can calculate kilowatts from joules and seconds, but you can't convert joules to kilowatts, since joule and kilowatt units represent different quantities.
The power P in kilowatts (kW) is equal to the energy E in joules (J), divided by 1000 times the time period t in seconds (s):
P(kW) = E(J) / (1000 × t(s))
kilowatt = joule / (1000 × second)
kW = J / (1000 × s)
What is the power consumption of an electrical circuit that has energy consumption of 90 joules for time duration of 3 seconds?
P(kW) = 90J / (1000 × 3s) = 0.03kW