How do I useOneDrive for backups?

[katymac]

I bakup regularly onto a USB

Can I use OneDrive for this weekly and do the USB once a month or so

Feeling a bit stupid about it all

The backup to oneDrive is continuous
www.windowscentral.com/windows-10-select-onedrive-folders-sync

So yes you can use onedrive for backups and as I'm paranoid copy to a USB once a week.

I mad ethe mistake that folders within folders aren't saved

Be warned that if you have a lot of files on Onedrive, it can slow your computer down considerably as it takes time to sync files.
I stopped using it for that very reason, and bought myself a large memory stick instead.