If you make word-based passwords, you still need to make sure to use random words. If you use a sentence or quote or song lyrics, then those usually have far less randomness than people think, and thus can be guessed easily by AI.

But if you use random words, a few words can be plenty secure. The diceware word list used by many password generators has 7777 words. 6 words means 7777^6^ possibilities, which is approximately 2^78^, aka 78 bits of entropy. That would take many years for any datacenter to crack. Though personally for really strong passwords, I go for 90+ bits of entropy.