If you can tell us what you have already done  (which has so far not worked) then perhaps someone can help or point you in the right direction.  Without that info, only people who can read minds over the internet can help.

The general idea is to add a Windows client to NetWorker, and use it to back up the NAS.  See KB article here:

https://www.dell.com/support/kbdoc/en-us/000191918/

this is exactly what i followed.

i have mapped the share from the NAS device as network drive and then followed the steps from this article but every time i run the workflow i get the error "no such file or directory"

Maybe a permissions issue?

Does the workflow at least get to this point?

  windowsbackupclientname.yourdomain.net:savefs The job has successfully scanned the file system on the host 'windowsbackupclientname.yourdomain.net'. The main save will now be started.

Just one more thing:

You mentioned "mapped network drive" in your question.

One is supposed to use the UNC path on the client configuration (on the "General" tab) - not a mapped network drive.

(I have one NAS backed up this way - the Windows client has no mapped drives at all)

@CrashCart​ Can you please post a screenshot from your general tab and apps&modules?

This is what i have configured in mine.

The device i want to backup is a Synology.

@CrashCart​

Does the workflow at least get to this point?

  windowsbackupclientname.yourdomain.net:savefs The job has successfully scanned the file system on the host 'windowsbackupclientname.yourdomain.net'. The main save will now be started.

Nope i don't see anything like this in the messages.

I suspect the problem is permissions.  It seems the job can not even read the "file system". 

My configuration is very much like yours.

A couple of differences:

 a) Remote user - in my case, it is a AD user, so it looks like this:

         mydomain\backupusername

This user needs to have admin level access to the share (or at least Backup Operator).  Not familiar with Synology, but there should be a way to grant this user Administrator or BackupOperator level access

b) Cross mount points enabled

Not sure if this was required (initial setup was quite a while ago, sorry), but it is checked in my case.