Hello,

So where do we start ..... :

First this is the wrong place to ask.

Second if you got hacked look how you got "hacked"
If you Installed a Malware or whatsoever malicious Programm I'd highly recommend scanning your PC.
Edit: I could bet on it you got added by a bot and clicked his malicous download link and downloaded the content.In this case your account (computer?) is controlled by the "hacker".

Third thing while you might be scanning your Pc , check on another trusted device (other than the one where you got "hacked") your account and email if you can access them , change passwords for both of them.

Fourth thing Go to Steam Support and create an account if you haven't already and make a ticket describing exactly when you got hacked , how it happened , what goods you lost and describing the actual situation.

Fifth Thing be Patient and wait a response from steam support and do what they tell you to do.

Might be missing some secondary details but hope it helps.
PS; never tell your password to anyone (anyone means ANYONE) for both your account and email account associated to it , because staff from valve would NEVER ask for your Passwords as they know everything from your steam account already (except email password)(I know it's stupid but this just keeps happening too often).

Tonculte

Feel free to add me to discuss this issue.