I just played this hand and thought it would be helpful since there is a 3-bet preflop and on the flop.

PokerStars No-Limit Hold'em, $0.50 BB (7 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

BB ($56.15)
UTG ($49.25)
spoonitnow (MP1) ($49.60)
MP2 ($25.50)
CO ($53.70)
Button ($50.90)
SB ($57.65)

Preflop: spoonitnow is MP1 with 7, 7
1 fold, spoonitnow raises to $2, 1 fold, CO raises to $5, 3 folds, spoonitnow calls $3

Flop: ($10.75) 4, 6, 7 (2 players)
spoonitnow checks, CO bets $6.60, spoonitnow raises to $18, CO raises to $48.70 (All-In), spoonitnow calls $26.60 (All-In)

Turn: ($99.95) K (2 players, 2 all-in)

River: ($99.95) 6 (2 players, 2 all-in)

Total pot: $99.95 | Rake: $3

Results in white below:
spoonitnow had 7, 7 (full house, sevens over sixes).
CO mucked Q, J (flush, King high).
Outcome: spoonitnow won $96.95

Pre-flop, CO's raise to $5 was a 3-bet. The first bet was the big blind posting his blind, the second bet was my raise to $2, and the third bet was CO's raise to $5.

On the flop, CO's raise all-in was a 3-bet. The first bet was his bet of $6.60, the second bet was my raise to $18, and the third bet was his shove all-in.

If you need any further clarification, don't be afraid to ask.