Hello,
You can translate admin strings using WPML admin strings option and add them to your string translator https://wpml.org/documentation/getting-started-guide/string-translation/finding-strings-that-dont-appear-on-the-string-translation-page/
Also, follow the WPML documentation https://wpml.org/documentation/theme-compatibility/building-multilingual-ecommerce-sites-using-xstore-and-wpml/?aid=46060&affiliate_key=YI8njhBqLYnp
Let me know if you still have issues with translation after that and untranslated strings.
Regards
