Question

How many paragraphs does the conclusion need to have

Answer 1

Its usually 1 because it should be brief and restates your claim in the introduction and doesnt need to have any details in it

Answer 2

In an essay it should only be one I'm pretty sure, but in a narrative as many as it takes to explain a lesson learned. If you were writing a book  your conclusion would be whatever comes to you and whatever you feel the characters would do/say/feel.