3 sets of wire in a switch box

I'm replacing a switch in my room, the old 2 way switch had all 3 blacks in the switch and the grounds bundled up and the whites bundled together I bought a 3 way switch I guess not knowing what I bought lol. Anyway I bundled the grounds and tied them into the switch and I'm trying to figure out where I'm supposed to put my blacks on the switch. Without killing power to my outlets when I turn my lights off.