Linux – mount: /mnt: unknown filesystem type ‘ext4’

I am trying to install Arch Linux on VirtualBox, however, when I am trying to mount the filesystems I get an error: 'unknown filesystem type ext4'.

I know there is a lot of people ran into the same problem and there's plenty of information available on the net but I can't seem to find a solution.

the output of fdisk -l:

Root@archiso ~ fdisk –l
Disk /dev/sda: 64GiB, 68719476736 bytes, 134217728 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x17c5711e
Device           Boot           Start          End              Sectors           Size                Id               Type
/dev/sda1        *               2048        411647            409600             200M              83              Linux
/dev/sda2                       411648     8603647            8192000            3.9G               82          Linux swap / Solaris
/dev/sda3                    8603648      134217727           125614080             59.9.G          83         Linux

Disk /dev/loop0: 403 MiB, 422539264 bytes, 825272 sectors

The error I get when I run mount /dev/sda3 /mnt:

mount: /mnt: unknown filesystem type 'ext4'.

By the way, how can I copy the contents of a command from VirtualBox Arch installer? I copied it the hard way! the mouse is invisible inside the ZSH and I can't use redirection > in order to save the contents as no filesystem is mounted.

Thanks.