Note: You will be able to translate these terms only for the languages which Chargebee doesn't provide the translation.
Here's how you translate them:
1. Download the language pack from Settings > Configure Chargebee > Customer-facing essentials > Languages.
2. In the pack, open your language's folder and you will find a file named "enums.csv" in the folder named 'internal'.
3. The enums.csv file will have different invoice keys where you can add the translated text to the value column of the key.
4. Finally, save the file, zip the pack completely and then upload it to your site.