I felt this same sense of “great, I’m an atheist now. So what next?” It went away when I realized there were so many new doors opened by a lack of god(s).Now you can explore who you are, what you think, why you think it, what you want out of life. Atheism doesn’t give you a purpose, it given you the opportunity to find it.
And to everyone here who says “Bah humbug, theists can’t be converted!”, to put it bluntly, you are wrong. I was a theist, who was arguing with atheists, and they ultimately convinced me there was a flaw in my logic and that I needed to reexamine my position. Am I an exception? Maybe. Could it be that your approach of “You’re indoctrinated fools who believe in idiotic fairy tails like little kids and you should stop it right now” is counterproductive? That’s also highly likely.