If God appeared to you and told you to ask for just one thing, just one thing and you would have it instantly. But also cautions be careful what you wish for because many have so wished for what has led to their own destruction. So think well and ask wisely.

What would it be, what is your greatest desire, what do you want here and now.

that he should prove his existence

Delafruita: that he should prove his existence

in that case u mean u urself doesn't exist?
Nothn exist outside God, so if u dnt exist dat means God doesn't exist.