@PitaJ
Thanks a lot
Now everything is working fine
Previously I was running nodebb version v.10.1 for last 1 year but when I try upgrading it to latest version
(before which i did mongodump first which results in making dump folder with two subfolders named admin and nodebb),
it kept me asking to install sharp first, which cannot be installed on centos 6 . So I changed my server to centos 7 .
Now the status is my new nodebb with latest version is running without my data
How can i use mongodump , so i can populate my new nodebb version with backup data ( most important )
Please guide me