A 2x2 pot doesn't leave much room for roots, so these sound like barely rooted cuttings. I wouldn't expect them to have enough reserves to survive the winter in a dark spot like your garage.

If you have an empty garden spot where you can plant them, that is one possibility, and they can continue on growing until it gets really cold in your area. Or a cold frame would work for them or a grow light set up indoors or in the garage. Regardless, you will need to replant them into larger pots if they won't be in the ground.

Or wait until next spring. I don't know what vendor you are using, but there are many reputable vendors of clematis and they all sell plants in the spring. Before ordering, you might want to look up other gardener's evaluations of the vendor you are planning to use on the Garden Watchdog to see if plants that small have a chance of thriving.

If clematis available during early summer then it 's a good news, may be I can wait until then. Thank you for your valuable comments.

While I would not buy those tiny plants to overwinter I have heeled tiny seedlings still in their pots in the vegetable garden for the winter and they have survived. With your warmer winter you might have success if watered regularily. The mail order clematis that I have gotten are well rooted before they are sent. I would check to see if those small pots are filled with roots and pot them up or plant them. With your warmer soil they may still have root growth during the winter.