Both, don’t find theme here: https://translate.wordpress.org/projects/wp-plugins/wp-show-posts/dev/nb/default or in the downloaded file wp-plugins-wp-show-posts-dev-nb.po file and can’t get it to work.
Renamed wp-plugins-wp-show-posts-dev-nb.po to wp-show-posts-pro-nb_NO.po and translate word i dreamweaver like this:
#: admin/post-type.php:22
msgid “Add New”
msgstr “Lag ny”