"We buy coffee from Cameroon."
Translation:Nous achetons du café du Cameroun.
You should read the Tips and Notes from the online version if you can't access them on your platform.
"du" is required with the meaning of "an unknown amount of a mass thing".
"du" is a partitive article used before masculine uncountable nouns starting with a consonant.
Whenever you can add "some" before a mass noun without changing the meaning, you can be sure the French will require a partitive article.
The feminine singular partitive article is "de la".
When the mass noun starts with a vowel sound (vowel or mute H), you will use "de l'"
- nous achetons du café, du vin = we buy (some) coffee, (some) wine.
- nous achetons de la viande, de la bière = we buy (some) meat, (some) beer
- nous achetons de l'alcool (masc.),de l'eau" (fem.) = we buy (some) alcohol, (some) water