"Where is my coffee?"
Translation:Где мой кофе?
It depends on the gender of the verb (by the way, меня=me, not my). мой is for masculine words (ending in consonants and sometimes ь), моя is for feminine words (ending in а or я, sometimes ь) and моё is for neuter words (mostly coming from foreign words that don't fit because they end in е о ю... etc.). However, there are LOTS of exceptions to learn. Кофе, according to what I've read, can be both neuter and masculine, but for some reason using it as a masculine word (so, with мой) is preferred.
By the way, it is well worth it to get some kind of textbook/pdf to learn the grammar. You're going to have nothing but headaches without some basic knowledge of gender, cases and declension.