We plan on taking a taxi from our hotel in Granada to the train station in Malaga. I can find a company on line.
That's a 1.5-hour drive, so a taxi would be expensive. See https://www.alsa.es/en/home for current bus schedules.
Unless money has little value for you why take a taxi when the bus is so convenient? The bus station in Malaga is next to the railroad station. Since it is close to two hours and the taxi is not going to get a return fare, I would guess the fare in excess of 200E and perhaps more.