Backup my account

I think someone has gotten in and done some messing up on my website. Silly me, I gave a guy my password etc. because he was helping me, but messed me up. I need to go back to the time before last and restore my website to this date. I need to know the date first, so I can copy my blog postings that I’ve done since then first.
[]Where can I see when this was
]HOW DO I DO THIS? Is it on my admin. panel, or in my website admin?
[]Where can I see when this was
]How do I restore my website to the time before last when I backed it up?
[*]Is there anything else I need to know?
I’m not a techi, just faking all this, so please use beginner language, step by step, please.

Thank you so much for the help,
Sue The “Accidental Leader”