In DS-160, what should I fill for date last visa was issued and visa number?

Hello, I came to USA on H4 in Jun 2013.And I applied cos for H4 to F1 in Feb 2014.It was approved in Aug 2014. Now,I am planning to goto India for some personal reasons and I have to get my F1 visa stamped there. My doubt is when filling DS-160 form, what should I write in date of last visa was issued and visa number?should I write my H4 issue date or F1 issue date? If I have to write F1 issue date what should I fill in visa number column (In my passport H4 stamping was there and visa number also there but it (H4)was expired.now am on F1 and have I-797A of F1,but I did not find any visa number on I-797A).and where can I find visa number on I-797A. could you help me please? Thank you.