https://github.com/PHPFusion/PHPFusion/tree/Tesseract/includes/classes/PHPMailer/language
Other languages you can find here: https://github.com/PHPMailer/PHPMailer/tree/master/language
https://github.com/PHPFusion/PHPFusion/tree/Tesseract/includes/elFinder/js/i18n
Other languages you can find here: https://github.com/Studio-42/elFinder/tree/master/js/i18n
Or if you download language pack you also get these missing files. E.g. https://github.com/php-fusion/locales/tree/version-8/Slovak/includes
Don't bother with English files. These translations are usually directly in code
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