When socrates says to meletus: if i believe in divine activities i must quite inevitably believe in divine beings, socrates tries to show that meletus accusation of atheism is inconsistent with his other accusations?

That statement is true

Meletus accused socrates of both being Atheist and Believe in Divine activities.

But both of those accusations cannot stand together, because if someone is an atheist, it won't be possible for them to believe something that couldn't be proven, such as divine beings.