$ sudo apt-get update
$ sudo apt-get install firefox-esr-l10n-sv-se 

firefox-esr-l10n-sv-se is installed in your system.

Make ensure the firefox-esr-l10n-sv-se package were installed using the commands given below,

$ sudo dpkg-query -l | grep firefox-esr-l10n-sv-se *

You will get with firefox-esr-l10n-sv-se package name, version, architecture and description in a table

firefox-esr-l10n-sv-se package basic information: