in baseball, teams play a series against an opposing team....it goes back to the insanely grueling 162 game season that separates baseball from every other major sport in the world....there are 162 games over the course of only roughly 180 games....needless to say, travel for these games has always been a bit of a concern, particularly since we are talking about cross country road trips
so typically, the season is broken into a number of 3 game series, though sometimes you will have 2 and 4 game series as well...so to answer your initial question, there will actually be 3 separate games played on each of those 3 consecutive days so you can choose whichever fits best into your schedule...you may want to wait to purchase tickets until you can get a better idea of who will be pitching (in that particular series, the best possible matchup would be if say chapman was facing off against harvey), what weather will be like, what else you will be doing. Getting tickets shouldn't be an issue as attendance has been down the last few seasons and there are always reasonably priced (and often great location) tickets available on a site like stub hub or even simply the mets website (i recommend stub hub bc as it gets closer to game day/time, you can often get some great deals on tickets
hope this was helpful and enjoy the game