I'm reviewing some of my hands while focussing on the cbet spots. This hand came up & left me kinda clueless.

6-max. The CO opens & Hero on BTN 3bets to 9bb - CO calls.
The flop comes 7dJhTh
Now I'm wondering what range (air, sets, overpair) I can cbet here with (given that villain is an unknown) & what is best to check behind (and the reasoning for this)? The board favours the CO's range so I'm inclined to play passively which is probably a big leak.

Thanks for the help