H1b Receipt Number

My H1b got approved on Nov2019 with my previous employer. But he didn’t share any details regarding my case. When i asked about my H1b approved case details, they said only at the time of stamping alone we’ll share all the details. I was waited for long time, but they didn’t give opportunity for US. Later i left the employer.

Currently, i got an opportunity with the present employer for US, they asking details about my approved H1b. But i have my only h1b approved start date and end date. Apart from that, i don’t have any details.

Is there any way to get my h1b case details and receipt number?
Is it possible to transfer the H1b with another employer, even before first stamping ?

Kindly provide your valuable comments to get my receipt number.
@anil_am22 anil_am22