Over 80 years and she is applying for B1/B2 visa

My mother is over 80 years and she is applying for B1/B2 visa. How can I go about scheduling an appointment for her? The waiver talks about the previous visa. She is a first-timer applying for a visa. Is she qualify for dropbox or will she go for interview? If yes to dropbox, how do I go about it, please? Under which category would the visa be?

Above 80 will be eligible for dropbox. You will apply under B2.

I have applied under B2. I have scheduled the appointment for dropbox but one of the requirements it is asking me to bring is Previous Visa, which I do nor have because it is my first time of applying for US visa. What do I do in this situation please?