Is your external WD drive your backup or is it the principal storage location for your files and photos? If there are files/photos or other docs on the WD drive that are not stored elsewhere, you will need another place for backups. What they are and how you get them there is really up to you.
I have an older WD MyCloud (EX4) with 6 TB of Raid 5 storage. It is my primary storage device. All my media, documents, virtual machines, ISOs, backups, etc. are stored on it. It has a 1.5 TB USB drive attached directly to it.
I also have an even old Netgear ReadyNAS with 2TB of Raid 1, plus an external 1 TB USB drive attached to it.
So my PC’s get backed up using an image based backup tool (Macrium Reflect). I back up my entire local drives (OS, Apps, data, etc.) to the MyCloud. I do this manually, but somewhat regularly.
Any pictures I take on my phone also get downloaded to MyCloud. Some may remain in iCloud.
My ReadyNAS is used to backup MyCloud. I don’t need to backup the backups, nor the many of the VMs. So only the content that’s important get backed up to the ReadyNAS. There is a subset of those get backed up to the USB drives. Periodically, I’ll copy a bunch of stuff to another drive and hand to a nearby relative to keep for me. I use the backup tools in the ReadyNAS to schedule these backups weekly. I can also trigger them manually if needed.
An even smaller set get backed up to the Cloud (google drive). These are mainly files I may need to access while traveling or need to share with others.
In the event I have to evacuate on short notice ( nearby fire, gas leak, chemical spill, etc). I can grab one or both of the USB drives. Given a bit more time I can grab either (or both NASs).
In the event of any hardware failure of any kind, I have at least 2 copies and possibly up to 6 depending on the importance of the file.
Bear in mind, I’m not running a business of any kind. My files are MY files, not anyone else’s. The vast majority of my content is really more of an archive and not docs in regular use. Other than photos, much could be replaced or recreated given time assuming I still need it. If 100% of it disappeared tonight, it would be a big deal but not catastrophic. What I have for backup is likely overkill for my needs.
So you need to decide what’s important. How important is it? What’s the impact if you lose it. Can you recreate, replace it by other means and how much cost/effort will it take.