How do I know emails from Facebook are legit

Hello, please help. I was hacked last night, I shut it down and opened up again with a different passwords a guy named hector just sent me an invite, I didn’t accept. A friend reported to Facebook someone was impersonating me. I received an email from Facebook that they’ve solved they caught it. How do I know these emails from Facebook are legit. Im too afraid now to go on anymore. ***@***