Well you know for sure that:
- Man send up a rocket big enough to go to the moon.
- There are a number of items indicating we went to the moon, including a lot of photos/video
- There has been many pictures taken of the lander
At this point, what evidence would convince you?
Try this for a starter. Take the best sci-fi movie from around 1970 and look at the special effects. Are they convincing? At the very least you have to allow for some amazing technological developments in special effects, whereas the moon landing was entirely possible using known technology (if you can get enough mass off the earth getting it to the gravitationally weaker moon is not much more difficult, and we can agree the rocket did go off earth).