Some stats for 3Bet pots are available for free download
here.
For those that aren't, what you want to do is find the stat you want and look at the Value Expression. It will almost always have two columns arranged like this:
(x / y) * 100
x and y are columns you can find on the columns tab. What you will want to do is duplicate and rename those and make some slight adjustments to them.
They are almost always of the form:
sum(if[X, 1, 0])
though X can be a complicated expression including ANDs and ORs depending on what you are looking at. To be certain that a player made a 3bet or higher make it:
sum(if[(holdem_hand_player_statistics.flg_p_3bet OR holdem_hand_player_statistics.flg_p_4bet) AND (X), 1, 0])
To make sure they faced a 3bet or 4bet:
sum(if[(holdem_hand_player_statistics.flg_p_3bet_def_opp OR holdem_hand_player_statistics.flg_p_4bet_def_opp) AND (X), 1, 0])
Save your modified columns. Duplicate the stat and modify the name, description, title, and value expression to use the new columns. Save, update your cache, and you are all set to go.