Did you contact Steam support?

Once you provide them with all the correct information it needs and you will get your account back in no time.

There is nothing that can be done here to help you. if the hacker hijacked your account with steam guard enabled, he

had to have access to youremail account as well.

https://support.steampowered.com

Also, You can add me on steam and I'll help you to get your account back.