How far would the Sun have to be to appear as dim as the moon?
The Sun appears 400,000 time brighter than the full Moon in our sky. How far from the Sun (in AU) would you have to go for the Sun to appear only as bright as the full Moon appears in our nighttime sky? Compare your answer with the radius of Neptune’s orbit.
I was going to answer your question until I finished reading it all. This is not an astronomy question. This a homework question. As such, it should be posted under the homework help category. Maybe someone there is willing to do your work for you. You already have all of the data required to compute the answer. Review your textbook to find out how to perform the calculation.
If you have others do your work for you, you gain no intelligence and only fall further behind when more complicated questions arise.
Good luck.
(Luminosity of the Sun is applied to the Inverse Square Law.)