$ sudo apt-get update
$ sudo apt-get install pkg-mozilla-archive-keyring 

pkg-mozilla-archive-keyring is installed in your system.

Make ensure the pkg-mozilla-archive-keyring package were installed using the commands given below,

$ sudo dpkg-query -l | grep pkg-mozilla-archive-keyring *

You will get with pkg-mozilla-archive-keyring package name, version, architecture and description in a table

pkg-mozilla-archive-keyring package basic information: