All existing data is retained during the upgrade process.
To upgrade please run:
yum install letsencrypt-cpanel
If you are not getting a new version, you may need to first run:
yum clean all
Please note, as per the WHM configuration in Home » Server Configuration » Update Preferences, the Let’s Encrypt™ for cPanel plugin will be automatically updated if the ‘Operating System Packages Updates’ option is set to ‘Automatic’.
More information on this option can be found here.