How to sync an iphone 6s without the passcode of the phone?

How to sync an iphone 6s without the passcode of the phone?

Added (1). My ex owns my money and I kept her Iphone 6s. I wanna sell it but I need to sync it first.
Any idea how to do that?

Only the owner can do that. The phone is useless to anyone other than the owner.

Theft is not a very sensible way to recover debts, especially when you steal a trackable traceable object which may also have a covert app installed sending photos of you and your surroundings back to the owner.

I understand your frustration but that phone is not the way to recover your debt and could land you in a huge amount of trouble.

There's an iPhone 6S?