The appraisal on the property should have been done already. It is actually one of the first steps in the loan process. As far as USDA is concerned, they need to have the appraisal and usually it takes 10 or less business days to get the loan approved and underwritten by USDA (that is if USDA has no condition that need to be met for approval). Best of luck to you and hope you get to move in asap.
What does your LO say?
What does your Buyer's Agent say?
What is the Loan Contingency on your Offer?
What is the Appraisal Contingency?
You realize the Lender cannot do a thing until they see the Appraisal?
Have you asked for an Extension on both the Loan Contingency and the Closing date?
Good luck and may God bless