Documents required for H1b transfer from India

I got my H1b visa approved this year, I got it stamped in January 18 and it’s validity is till September 2020.

I came to US in Feb 2018 and I have been looking for job through my employer but no luck yet. Now I have to return to India because my father is not doing well.

I am not happy with the empoyer and hence would like to change my empoyer when I am in India. So, I would like to know what all documents will be required for H1b transfer. I have original I 797 B copy with validity till Sep 2020 but I don’t have any offer letter, pay stubs from my employer. Please help!