Scared to format my computer hard drive

Hello everyone,

I am working on a computer with a 500GB local hard drive.

I try to mount a new external hard drive with the same size of 500GB.
As this hard drive has not been recognised, I try to mount it manually.
To get the list of the disks on my computer, and how to format the new drive, I have referred to this post:

https://www.linuxquestions.org/quest...5432746-print/

The outputs of the command Code:sudo fdisk -l are partially the following:

Code:Disk /dev/nvme0n1: 477 GiB, 512110190592 bytes, 1000215216 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: gpt
Disk identifier: 0C9EA23F-EAC6-4197-94CE-E92CA9EF476D

Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 1050623 1048576 512M EFI System
/dev/nvme0n1p2 1050624 1000214527 999163904 476.4G Linux LVM

Disk /dev/mapper/ubuntu--vg-root: 475.5 GiB, 510543265792 bytes, 997154816 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

Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4096 bytes / 33553920 bytesWould you know which one is the external hard drive?
I am afraid to format my computer hard drive as they all have the same size!

Thanks for the help!