NL50: 3bet pot, second barrel?

[M.P.Rator]

No-Limit Hold'em, $0.50 BB (6 handed) - Hold'em Manager Converter Tool from FlopTurnRiver.com

BB ($56.85)
UTG ($50)
MP ($29.60)
CO ($50)
Hero (Button) ($50)
SB ($24.50)

Preflop: Hero is Button with :8s, :7s
2 folds, CO (poster) bets $1.50, Hero raises $6.50, 2 folds, CO (poster) calls $4.50

Flop: ($13.75) :tc, :kc, :6h (2 players)
CO checks, Hero bets $9.75, CO calls $9.75

Turn: ($33.25) :ad (2 players)
CO checks, Hero bets $18.50, CO raises $33.75 (All-In), Hero folds

Total pot: $70.25

villain: unknown

mal abgesehen davon, dass man gegen unknown so eine hand nicht 3betten sollte, wie spielt man diese hand richtig?