IF your 'Mac Mini Late 2012' computer - most shipped with Mavericks 10.9.x and won't run
newer version third-party software, then an upgrade to El Capitan 10.11.6 should do nicely.
Or further upgrade ~ if you have read about the issues; make suitable precautionary backups
and then hope you get lucky with High Sierra. At least you may be able to revert w/ backups.
Last Sept 2017 finally I chose to upgrade from Mavericks 10.9.5 to El Capitan 10.11.6 and
made a partition on original 1-TB HDD for second OS X install. It works OK. So it has two
OS X and dual-boots. And have 2nd internal HDD, in this server model, for other uses.
You have options because there still a link to get Sierra 10.12 from an App Store page.
• How to download macOS Sierra - Apple Support
{Reading though I've noted some Late 2012 Mac mini i5 and i7 users have issue with macOS
10.13.x High Sierra due to some graphics problem and some other performance complaints.
The graphics is built-in, and noticed El Capitan gives the GPU a higher output resolution, with
the same chip-set. I've used the same display; w/ max upgraded standard RAM before OS X.}
So you could test the waters 'one foot at a time' least there be swamping due to an under-tow.