How to restore iPhone 3GS?

[JohnPyn]

Hi everyone, here's the situation... A friend gave me an iPhone 3GS that I need to use until I get back my 6 plus hopefully repaired since the Touch ID was working erratically... But I can't restore it... I have no idea what firmware it has but I'm thinking of iOS 5 possibly but not sure at all... The power button is broken and it doesn't work. I've tried redsn0w but it requires me to put it in DFU mode but I can't because of the power button and iTunes won't let me in it since it's protected by a password and obviously to make everything harder since she last used it like 1 year or 2 ago... Or more... She forgot the password... What can I do? Please I really do need help