H1b transfer without stamping after 6 yesrs

My petition got approved in 2018 with employer A but it was never stamped now new employer is ready for H1B transfer however I have only case number and form i129 but no approval copy of 797. Is H1B transfer is possible after 6 years without 797?

Your immigration lawyer can include a letter with the copy of I-797 receipt and I-129 with the new petition. Your case approval should be on USCIS record and they can look up.
Other option is to request the approval copy from your employer who originally filed your H1B.
Yes the new employer can file a cap-exempt H1B petition based on prior approval, no limit on time.

Thanks @Kalpesh_Dalwadi for your response. I have tried reaching to my previous employer and they are not ready to share the details. If receipt copy can work then I can proceed for H1B transfer. Other thing, there is no time limit so it means even it been more than six years and transfer is still possible