The sun is 92.96 million miles away, give or take depending on the time of year, obviously. The moon is about 238,900 miles away, again, depending on the time of year.
I'll make the argument. The Moon is verified to be 200000+ miles away because we landed on it. Rockets work in space, they have been proven to work in space, and they have worked in space. If you don't believe it, either you don't understand introductory physics or you're too lazy to do some very basic experiments. By all calculations involving Newton's laws, we can (at a rather astronomical cost) send things into space, and to the moon. See the derivation of the Tsiolkovsky rocket equation. So the burden of proof is on Flat Earthers to prove, that despite rockets working on paper, that they can't work in practice because of some unsolved engineering challenge. If you don't understand rocketry, please don't insult the thousands of engineers who work long days to put stuff into orbit with misguided physics. This is why people laugh at those who say rockets don't work in space; they are criticizing engineers and scientists who use very advanced math and physics by using fundamental and easy-to-spot physics misconceptions.
The Sun has to be 93 million miles away, because otherwise it would burn up the Earth with its immense amount of solar energy. I know that FE theorists have a counter to this, saying that the Sun is 32 miles wide. This is bollocks. I didn't mean it as a joke or vacuous truth when I said if the Sun were 32 miles wide, I could build a thermonuclear bomb in my backyard. We first note that the Sun needs some way of producing energy, and the only plausible mechanism is nuclear fusion (my physics textbook ballparked the Sun's lifetime at 10000 years if it just went off thermal energy). We also know that nuclear fusion only occurs under certain conditions, namely that the particles of the fuel plasma need to collide with a certain amount of kinetic energy. The Lawson criterion provides rough estimates for the temperatures and pressures required for nuclear fusion. A 32 mile wide Sun will exert such low pressure (even lower because FE theorists contend that gravity doesn't exist and there's only a small amount of attraction between matter) on its core that I can replicate it in my backyard with some power tools (or chemical explosives). Water would be the biggest WMD devised. Of course, Tom Bishop said that stellar fusion has never been tested on Earth. This is a blatant lie. We have tested fusion conditions on small amounts of matter and have concluded that the fusion criteria are correct. Teenagers have built homemade inertial electrostatic confinement reactors. I hate to keep repeating the same stuff, but it seems like this never gets absorbed or rebutted by FE people.