What version of macOS should I update to, and how do I go about it?

So I'm currently on a 2011, 27-inch iMac that is running macOS Monterey 12.7.6 using OCLP.

I have a update in the settings app for MacOS Tahoe 26.4.1 - but I know I shouldn't update straight from the settings app.

I was wondering what's the version I should go up to on this iMac - and how to go about updating to it without losing my data and files as well, thanks.