Hi Lacey, I'm guessing it's an SQF audit.
You say you passed the desk audit, so that's a good start.
If the documented procedures reflect what happens in reality (pretty much) you should be fine.
The auditor will be experienced and lead the audit, it's not an exam, you just answer questions, show documents and take the auditor where he/she wants to go. It won't be perfect (it never is), there will be errors and omissions and gaps and you will learn new things that will help you improve your FSMS. That's just continuous improvement. You won't fail unless there is one or more things that present a very serious and imminent risk to food safety.
Hang on in there, use the three weeks to test and find potential NC's, remind employees over and over and chill out.
It will all go fine...you'll see...and when it does come back and tell us.