I’ve grown them in 5 gal buckets outside all summer. It gets extremely cold her. Zone 2b or 3 I believe.
You can take cuttings and start new plants to grow inside over the winter. They will need as much light as possible.
https://www.gardeningknowhow.com/edible/herbs/mint/growing-mint-indoors.htm
I have a large peppermint plant in a pot outside. Can I separate it and leave some of it in the garden over the winter?
It is often recommended to take cuttings and root them inside for the winter, rather than bringing in a whole plant. If you leave part of it outside, it may not survive the winter. Peppermint is hardy in USDA zones 5-9 and you are right on the edge.
If you prefer, you can dig up part of it and replant it to bring inside. Make sure you check for bugs before you bring it in. Be sure you bring it in before a frost is predicted.
https://www.gardeningknowhow.com/edible/herbs/mint/growing-peppermint-plant.htm
https://www.gardeningknowhow.com/edible/herbs/mint/growing-peppermint-indoors.htm