Unzip your backup dir somewhere convenient where you have full read/write permission as your normal user account.
Assuming that the c:\users\myusername\desktop\postgresql folder contains the folders named bin, data, lib, etc:
Open a cmd shell
cd C:\ManageEngine\OpsManager\postgresql
bin\pg_ctl start -D C:\ManageEngine\OpsManager\postgresql\data
psql -U postgres -h127.0.0.1 -p13306 OpManagerDB
#for other Postgres DB you might not need to list the port/ip ( no -h -p )
If psql connects OK disconnect with the \q command then promptly make a dump of the database:
bin\pg_dump -Fc -U postgres -h127.0.0.1 -p13306 OpManagerDB -f mydb.dbbackup mydb