+1 to what Howard said about backup of the site ... that's code directory, DB dump, and moodledata directory.
Docs for site backups: https://docs.moodle.org/30/en/Site_backup
IF you don't have many courses, I'd suggest one step further ... full backups of courses and download those backups ... or send them to a designated directory on the same server where hosted (can do if you have Linux and ssh access to server).
However, having said that, do run the environment check on your current setup. Update the component and then in the drop down list select the version to which you will be upgrading (3.2) see if your server meets requirements for the target version.
There *might* be upgrades to PHP or DB changes or ? needed to assure your upgrade will go smoothly. Much of that dependent upon where hosted and, of course, your ability as the server admin. You run across anything you are not sure about, by all means come back and ask. When/IF you do, please share some more info about your setup ... Linux/Windows - hosted how/where, PHP version, MySQL version - DB settings, etc..
'spirit of sharing', Ken