vCenter 7.0 and NetBackup 8.1(Appliance version 3.1) incompatibility Issue. Backup Fails!

Hello, 

First of all, I'm not familiar with NetBackup.

I just noticed that all VMware VM backups fail after I upgraded vCenter from 6.7 to 7.0. 

NetBackup 8.1 console> Media and Device Management> Credentials> Virtual Machine Server, the login to new vCenter fails, which I think why all VM backup fails. 

NetBackup Core Support confirmed that this is incompatiblity issue and I have to upgrade my Appliance and the other media server and Netbackup to upper version. 

Can anyone layout the steps and links how I can perform this upgrade? I searched knowledge bases but Appliance white papers talk about only appliance, Netbackup talks about only netbackup upgreade. 

Much Appreciated in advance.