WordPress uses PO and MO files to manage translations. In fact, WordPress only needs MO files to handle translations.
Translations can be filed in the
Hypermarket theme will look in this directory for translations as a fallback.
It is however recommended that you use the global WordPress language directory and install your translations like so:
That way they will not be lost or overwritten during Hypermarket updates.
Alternatively you can put translations in your child theme:
More information can be found on the documentation.