I think I have a Leviton double pole dimmer switch. It used to operate track lighting along with an on/off light switch in the same room (different entrance). I replaced the track lighting with a fan which has a light and "integrated" dimmer capabilities (via a remote control). I need to replace that dimmer switch with an on/off light switch. The dimmer switch has three wires (it was installed in 1985). On one side, there is a red and black wire. The dimmer red wire is connected to a black wire from the wall and the dimmer black wire is connected to a pink wire from the wall. On the other side of the dimmer, there is a black wire that is connected to a black wire from the wall. I believe I purchased a double pole on/off light switch. How do I connect it? Thanks.

You mention a dimmer and a 2nd on-off switch.
You purchased a 'double pole' switch which I believe is a 3-way switch.

3-way switch has 3 screws (plus ground screw which will not be mentioned further)
3 screws on 3-way switch = one is dark colored, and 2 are brass colored.

You can guess. There are only 3 wires and you can keep trying different combination until both switches work. Do not change wiring on 2nd switch and sooner or later the right combination will appear.

On the other hand, electricians test wires using ordinary tester, before connecting anything.
If you want to test, it takes 3 ez steps.

Here's what I would do.
1) Look at wiring on 2nd switch.
Notice switch has 1 dark screw and 2 brass screws.
If you can identify the two wires on the brass colored screws, these are the 'travelers' and same two wires connect to brass colored screws on new switch. And then last wire connects to dark colored screw.

2) You have noted the wires carefully on dimmer, so remove dimmer, and separate wires for testing.
2nd switch is moved to down position.
We are NOT going to test wires on 2nd switch.
We are just testing wires at old dimmer.
Turn on power.

Power is on.
2nd switch is in down position.
Test each wire to bare ground wire.
One and only one wire will light up the tester.
Mark this wire.

3) Change 2nd switch, and move 2nd switch to up position.
Test each wire again to bare ground wire.
Again only one wire will light up tester.
Mark this wire.
If same wire lights up tester each time, then this is the Hot wire and it connects to new switch dark screw. And the other two wires go to brass colored screws.
If a different wire lights up each time, then these two wires are 'travellers' and they connect to each brass colored screw. And the last wire connects to dark colored screw.