Not backups. If you store files, pictures on an external and it is your only copy, it is neither stored or backed up.
A backup is copies across a few devices and places. The only storage I know of is on say DVDs that are not erasable.
For now, copy your files up to say some memory stick or cloud (there are so many now) so that when you prepare your new drive you don't lose your files.
As to Seagate backup the app, I don't advise its use. I like SYNC apps that do not store in proprietary ways. For example, Roadkil's Unstoppable Copier.
I have an external hard drive that I am using to store photos (this was a back up drive but I just turned that function off). I bought a new Seagate back up drive and when I set it up it doesn't show the external hard drive as an option to back up. How do I do that? I found a tool to partition the whole storage drive but I am afraid that would delete my photos or cause more problems than it helps. Not even sure I understand what partitioning would do. I truly need those photos backed up!!!!