Judging by the experience you have had do you really want to chance things again with VM agents in this country or in India. I suggest not.
But we can help. I will link you to help files that VM publish. You need to read them carefully and carry out each instruction without fail. The reason your mail has been deleted and you can't get it back is that the hackers have got into your VM web mail and done this. So it is vital you follow all the steps to get your web mail cleaned up. The mail has gone for ever.
The blackmail threat is just a frightener. Go the Action Fraud site and report it there if you must. But it is awell known scamming attempt. They don't have your current passwords, just old one they have gleaned from sites they have hacked. IF they do have your current password you have some work to do in making sure your new passwords are secure.
Superuser 18/19. Use Kudos to say thanks Tick an answer as "helpful" only when the problem is solved Please don't send me private messages unless I ask you to. I do not work for VM. The advice I give is based on my best understanding of VM policy and practice. You rely on it at your own risk.