Each game is an independent event with it's own probability of a team winning based on unique factors associated with that game.  The probability of winning all 3 events (or 2 of the 3, or 1 of the 3) is considered a joint event, as it is joining multiple independent events together.

The probability of winning all 3 is the easiest to calculate as it is simply the product of the probability of winning each independent event.  For example, if the probability of winning Game 1, Game 2 and Game 3 is 50%, 75% and 35% respectively, then the probability of winning all 3 games is 50% x 75% x 35% or 13.125%.

Based on the probabilities of winning 1 of 3, or 2 of 3, can also be calculated but are a little more complex.

All of this assumes using the "frequentist" method of statistics.  Using Bayesian statistics is another approach, but beyond my desire to discuss right now.