I assume you meant that the Moon is about 240,000 miles from Earth, not 240,00 as you have written :) Well, the answer is: the Moon is about 24 * 10^4 miles from Earth.
Just write 24 and multiply it by 10 to the power equal to the number of zeros (if there are four zeros after 24, then multiply it to the 4th power of 10).
