Which game?  

"Game" in opener’s Major suit

If you have 3 cards in your partner’s opening major suit, you have at least 8 trumps between you. Partner has promised at least 5 with the opening bid (majors only). Having 8 trumps is called a FIT. If you have a fit in a major, that is likely to be the best place to play your game (26 TP's and a fit in trumps between you and your partner).

"Game" in Notrumps

If you don’t have 3-card support for your partner’s major suit, you should usually bid 3NT - needs 25 HCP's between you and your partner

"Game" in opener’s Minor suit

Because 9 tricks in 3NT scores the same as 11 tricks in 5C or 5D, minor suit games are less common. If 5 of a minor makes, then is likely 3NT will also make. Making more than 9 tricks in NT gives a better score - needs 27 TP's between you and your partner