Permissions problem USB Backup Plugin

Hello everyone,

I'm having some problems when simulating a "crash" and trying to restore from the External USB drive that I have set up to backup with USB Backup Plugin.
I'm trying to mount it on an Ubuntu 16.04.1 Virtual Machine to try to recover the files in an event of a crash of the OMV system but I'm unable to access the drive. Ubuntu says that I don't have permissions to display the files in it.
How can I recover the files in there if my OMV box is dead or simply I want to grab a file from the backup drive from another Linux distro?

Drive is formatted as ext4 and plugin works wothout problems: I plug in, it runs and then it unmounts the drive and I disconnect it and store it in a safe place.

Thanks in advance!

PS: I add a screenshot of my settings

Yes. Since I'm not a Linux guru (yet), I open the file mànager and double-click "Extern" (label of the HDD) and then it complains about permissions.

So you telling me that I should mount via CLI as root? I'll try tomorrow; 23:55h here and I'm going to bed.

Thanks for the hint!

No luck @subzero79.

Mounted but inaccessible because of permissions.

I ran:

$ sudo mount -t ext4 /dev/sdb1 /mnt/extern

But same output when I try to open it: I don't have permissions to display the files.