Seems like you skipped a couple/few steps.

I.e.:
What is (your best guess at) a typical reg villain's range to open 3x from CO, here?

(What is your 3-betting range in this spot?)
What's your range to flat call in this spot?

What is your range to check on this flop?

What is (your best guess at) Villain's range to check behind OTF?