When choosing a target language to translate, the app will show you a list like this:
That list is the languages that are supported on Shopify, if you can not find the language you want, that is because Shopify does not support that language at the moment.
For a solution, you can choose a second language which is mainly used in that country to translate. For example, Philippines use two main languages, which are Filipino and English. Although Filipino has not been supported by Shopify, you can choose English as an alternative option for your translating.
Hope this article can be helpful for you, should you need any further support, feel free to contact us via live chat or email firstname.lastname@example.org
Have a nice day!