You see what version of the database you’re running and look at the database templates to see what version they are upgrading to.
One way to see what version you’re running is
./launcher enter data
psql --version
There are a bunch of topics about the last database upgrade, about 6 months ago (but it might have been 3 or 9). As much as I see you here in surprised you missed it!
And if disk space is a problem then the database upgrade will be challenging because you need at least 2x free space since you’ll be making another copy of the database to upgrade it.