Which method is best for testing final version of the website

I'm new in usability testing and I need to arrange a usability testing on final version of our website. I'm not sure which method of testing is best in this occasion? Do I need to go to street and show the website to people and see what they think? or do I need to arrange moderate testing. I think I need to arrange moderate testing and choose some task and sit with people and see if they can finish the tasks and ask them what they think about the UI at the end of the session! Please let me know if I'm right or wrong and any suggestion will be appreciated!

Thank you so much.

Milly