Using btrfs backups on new install

[oldgeek]

One other question I forgot to put in: will the backup @ subvolume cause any problems in the new install if it replaces the new @ subvolume, which contains newer versions of the 18.04 programs?

[oldgeek]

I'm a little confused on how to use the backups of @ and @home on a new Kubuntu install. I have made backups on an external hard disk of my latest @ and @home subvolumes, each with the date, time and ro additions to the titles of each. I want to erase my Kubuntu 18.04 and change to Kubuntu 19.10, which I like a lot (tried it on QEMU VMM). I want to use the whole hard disk for this, as I do not use Windows anymore. How do I transfer the @ and @home subvolumes on my external HD to my new install? I know I have to do some renaming, but despite some research on this I haven't been able to deduce the exact sequence of commands I need to make. I have the BTRFS Subvolume Manager installed on Dolphin, if that's any help. What confuses me is that I don't know the difference between rolling back and replacing new @ and @home subvolumes with my backups. I don't want to mess this up, so I would appreciate any help someone could give me.