Yes, you gather it from the context in this case. Some masculine and neuter words don't form the plural any differently (no ending or umalut). The plural of "der Teller" is "die Teller", and it's only the "the" word that lets you know.
Out of curiosity, would the English sentence "I will (I'll) have two plates with rice" in German be "Ich werde zwei Teller mit Reis habe"? There might also be a couple of extra "N"s to imply future tense. Have I got that right?