Sales Report Email has built-in support for the WPML plugin. Note you will need the WooCommerce Multilingual as well as WPML, together with the String Translation and the Translation Management modules, which are part of the Multilingual CMS package.
You can add more languages from WPML > Languages, There you need to click on Add / Remove languages, then find the languages which you want to add for translation.
After adding the languages, navigate to WPML > String translation, there You can find a dynamic string by search and you can filter a string by the plugin. you can do a translation of a string by clicking on the edit icon in a particular language.