There is no password.
When you created wallet on Myetherwallet you got your keys, you probably save them to your PC.
Because you have used them at least once to check your balance?
So the question you must ask yourself did you ever opened your wallet after initial creation, if not there is a good chance that you never downloaded your keys in the first place.
If you know your private-key you won't need anything else to log in to your wallet (just like the recovery phrase).
The keystore-file is your encrypted private-key which additionally requires a password to access your wallet.