How do I save plants if I put them in our garage?

If your garage is heated and stays at a temperature that the plants will survive your plants should be ok. My garage temp can go down to 0 degrees or below in the cold winters here. I keep one part of my garage heated to 40 degrees and I don't know if that's even warm enough.

I always put my plants in the garage in winter. Here are my instructions for a hibiscus, but this can apply to all other potted plants too. Sunlight is important, so if your garage is like mine and has no windows, getting them outside occasionally on a sunny day helps. If you have really cold temperatures like mentioned above, you can heat it a bit. It’s okay if it’s not very warm, keeping plants out of elements and moisture helps. Here is the link on how I prepare my plant to bring into garage: https://chemistrycachet.com/how-to-take-care-of-potted-hibiscus-in-cold-weather/

Also along with the low heat check once a month to see if the plant(s) need any water. Give it a bit to keep the roots healthy and gradually give more in the spring.

If there is a window that affords sunlight, then by all means put them by it if possible. Wrap your pots with old towels or blankets to keep root balls from freezing , then water sparingly throughout the cold season. Best of luck.