$ sudo apt-get update
$ sudo apt-get install kubuntu-notification-helper-db

kubuntu-notification-helper-db is installed in your system.

Make ensure the kubuntu-notification-helper-db package were installed using the commands given below,

$ sudo dpkg-query -l | grep kubuntu-notification-helper-db*

You will get with kubuntu-notification-helper-db package name, version, architecture and description in a table

kubuntu-notification-helper-db package basic information: