Before you update, it’s best to make a full site backup and make a database backup. This will ensure you can revert to a working version if anything unexpected occurs.
There are some great plugins to help backing up your site:
VaultPress – A monthly subscription based service developed by Automattic, the company behind WordPress.com.
BackupBuddy – A paid and premium WordPress backup and site restore plugin developed by iThemes
BackWPup – A free WordPress backup plugin with a paid Pro version, as well.
All-in-One WP Migration – This plugin exports your WordPress website including the database, media files, plugins and themes with no technical knowledge required.