There are several species of Mirabilis. Some are hardy, but the most commonly grown one is Mirabilis jalapa, commonly called 4 o-clock or Marvel of Peru, and it is not hardy in Zones colder than Zones 10 and 11.
You can dig the tubers and store them in sphagnum moss or vermiculite in a cool, dry location. Temperatures around 50 degrees are ideal.
It's also quite easy to start 4 o'clock from seed, so you may want to simply collect some of their seeds and plant them from seed next year.