Dropbox documents for F-1 visa renewal

I am traveling to India to renew my F-1 visa. I qualify for interview waiver according to the questions on cgifederal. In the drop off documents, I am supposed to provide a photocopy of I-797 form. As a previous F-1 visa holder, I have never filled or received this form. What is this form and how do I obtain it for F-1 visa?

Thank you.

I-797 is provided by USCIS for people who are already in the US and changed their status from another non-immigrant status to F1.
In your case you can use the I-20 issued by your DSO and other supporting documents for visa stamping. Talk to your ISSS/DSO and they will help you with new I-20 with travel authorization.