You can make a ballpark estimate of Jupiter's synodic period if you know that Jupiter orbits the sun once every twelve years, while Earth orbits in the same direction in one year. So when your Earth calendar has completed a year, Jupiter has moved approximately one-twelfth of the way around its orbit, and Earth has to move approximately another month to catch up. That gives you a synodic period of about thirteen months, consistent with the more careful calculation by Mike G.
The ballpark estimate doesn't work very well if the periods are too similar (e.g. for Mars or Venus), but it's fine for the outer planets.
As to when you can see it again, Jupiter's next solar conjunction is on 2021-01-28. So if it disappears into your evening twilight at the end of December, you should expect to find it in the morning twilight around the beginning of March.