How do you say interpreter in Spanish?

It depends on your "method of acquisition".

If you are going to hire an individual or bring on an individual whose job it is to be an interpreter, you would say: "Contrataré un interprete" -- literally, I will hire an interpreter.

If you are simply going to call a friend or co-worker that can function as an interpreter, but is not in the usual occupation of being an interpreter, you would say: "Encontraré un interprete" -- literally, I will find an interpreter.