Q.Where can I get spearmint plants?
Don’t know where I can find spearmint plants.

Certified GKH Gardening Expert
Try local garden centers, even your local grocery store generally sells some culinary herbs in pots in their produce section.
If you know another gardener in your area; ask for a cutting and start a new plant.
Mint can also be started from seed; there are many reputable seed companies listed on the internet.
https://www.gardeningknowhow.com/edible/herbs/mint/how-to-grow-mint-plants-in-your-garden.htm
https://www.gardeningknowhow.com/edible/herbs/mint/how-to-plant-mint-seeds.htm