How to restore an index

We have accidentally deleted an index through Cerebro. But we have backup of that deleted index folder from server backup. Could you please let me know how to restore that deleted index from that server backup?

Please help me on this

Restoring from file system snapshots is not supported. The only supported way to backup and restore Elasticsearch data is through the snapshot and restore APIs. I therefore doubt there are any instructions available and if you are on Elasticsearch 7.x I as loo brlieve it is impossible.

Can we use recovery API for the back up folder to restore my deleted index?

That can only be used against snapshot repositories created through the APIs.

Am using Elastic search version 5.3.1. Can you please help me is there a way to restore that index from the backup folder?

As it is not a supported way to restore data it is not something I have ever tried, so I can unfortunately not help.