How to convert kWh into watt and joules?

W= 1J per second
kW= 1000J per second
1h = 3600 seconds
then,
1kWh =1000*3600
12kWh = 1000* 3600 * 12

Hello DkE, let us brush up the fundamental first.
Joule is the unit of work or energy.
Watt is the unit of power which equals to J/s ie work performed or energy spent in one second duration.
kW is kilo watt. kilo stands for 1000 or 10^3.
If we need energy given out by an engine with power P in time t then E = P*t
So J can also be taken as W s.
Now in one kW has 1000W. one hour has 3600 s.
So kwh ie kilowatt hour would have 1000*3600 Ws = 36*10^5 J
Hence 12 kWh means 12 times 36*10^5 ie 432*10^5 J or 4.32*10^7 J
NOTE: kWh and W are having different dimensions. SO we cannot get W from kWh.

Watt means joule per second.
k means kilo = 1000
h means  hour = 60 minutes = 3600second.

Hence
1kWh means 1000* joule/second* 3600second = 3600000 joule.

12kwh = 12*3600000 = 43200000 J
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12 kWh on a day   means 43200000  joule per day.
Hence answer for the question
"How many joules is this?" is 43200000  joule  
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12 kWh on a day   = 12 kWh in 24 hour.

Average power is  12kWh / 24 hour = 0.5 kW = 500 W
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