I am replacing a very old three switch system and updating it to combo 3 rocker switch. These switches control the front porch light, entryway light and a living room light. The old switch was not using the white wires as they were capped. It had one red and two black wires wired into the left side of the old switch on their own screws. The right side had one black curved and exposed in three places to wire into the right side of the box. The new switch has only one left side screw which is for the Hot Black. The right side has three screws and it instructs you to wire your three blacks AND three whites to these. How should I proceed and what do I do with the red wire?
There are different ways that lights and their switches get wired.
If all of your whites were capped individually this means that the light's neutrals are being tied in at that light fixture.
If all of the whites are tied together then each fixture is being fed it's neutral from the source at the switch box.
The common hot is wired to the common terminal of that particular switch.
The common hot then feeds the three lights through black, black, and red in your case.
You should open the fixtures and look at the wiring just to make sure.
Why did it say to wire your whites to the switch? Sometimes white is used as a switch leg if the neutral is being supplied at the fixture rather than at the switch. Which is why you should look at the wiring at each fixture.