Answer:
a billion (1,000,000,000) gremlins
Step-by-step explanation:
since 1 milliwatt is 0.001 watt you'd need 1,000 gremlins to produce 24 watts
since 1 megawatt is 1000 watts you'd need 1,000*1,000 = 1,000,000 gremlins to produce 24 megawatts
to produce 24,000 megawatts you'd need to multiply that for another 1,000
so 1000*1000*1000 = 1,000,000,000