You have to prepare scheme of arrangement u/s 391 to 394 of Companies Act for merger and get the same approved by High Court. A standard checklist shared by some friend is attached for reference.
Dear Agrawal Ji,
I am not able to download attached file. You may pls be required to email the attached file of checklist of merger and amalgamation on my email id : nehajaincs @ gmail.com
Regards.