howto install l10n autofetch
The l10n update extension has not been compatible with CiviCRM since version 4.7 of CiviCRM was released in 2016 there does not appear to be any concerted effort underway to bring this extension up-to-date for CiviCRM 4.7+

Source: https://github.com/cividesk/com.cividesk.l10n.update/issues/3

You can still install language packs into CiviCRM as before: https://wiki.civicrm.org/confluence/display/CRMDOC/i18n+Administrator%27s+Guide%3A+Using+CiviCRM+in+your+own+language however the l10n files will need to be updated manually when CiviCRM itself is updated.