Updating a fresh install of Nextcloud

Hello there, friendly internet people,

After flashing the ubuntu-standard-16.04-server-armhf-rpi2Installer image from October 18, 2016 onto my nextcloud, everything worked well enough until I tried to update Nextcloud (since that image comes with Nextcloud 10.0.1 I think. I encountered a write-permission error that I fixed with the chown-fix that was offered in this forum. I also used sudo snap refresh afterwards because my intuition was that that might also help. (I should mention at this point that I only have a fairly basic understanding of what I am doing here, unfortunately. I’m happy to learn more, though, which is part of the reason why I got a nextcloud; learning by doing and stuff.)

After accessing my nextcloud again, it didn’t offer to sign in at all, instead saying “yo, let’s update to version 12.0.4” which surprised me because I was initially running version 10.0.1 and that seemed like a pretty steep update. But since I didn’t have another option, I hit that update-button and was hoping for the best. That didn’t help, though, I only got the message “Exception: Updates between multiple major versions and downgrades are unsupported.” The forum post regarding this message was somewhat helpful. The problem is: it says “Remove all files and folders of your Nextcloud installation folder except /data/ and /config/” which is straightforward enough. Using the image that came with a nextcloud installation, however, I’m not 100% sure where the installation folder is. There’s one in the snap directory but that one doesn’t have data and config directories. I’m a bit lost at the moment. Where is the original installation folder in which I should put the 10.0.5 file to update?

Sorry for the amateur-ish questions. Your help is greatly appreciated, though!