To keep mold out of your unused refrigerator start by cleaning the refrigerator out good and drying it and then place an open box or 2 of baking soda on the shelf and you can even keep the doors open on the refrigerator to allow ventilation.
Placing ice packs on the refrigerator shelves can also help prevent mold growth in the unused refrigerator as the ice packs will absorb moisture.
If leaving on vacation and you have no food in the refrigerator you can unplug it to save electricity.
You should unplug your refrigerator if away for 1 month or longer.
Removing all the food and unplugging the fridge will also save electricity and you will return to a clean fridge.
Wipe down the inside of the fridge with a rag and prop the door open to allow ventilation.
If you are going away for a month or longer, it is always a good idea to unplug your refrigerator to save on your electric bill.
Empty your refrigerator, drain the water tank if you have one, clean the inside of the refrigerator and leave the doors open to avoid any unwanted odors.
A freezer can be left plugged in and should if you have frozen foods as frozen foods can last longer and the electricity saved in that instance is not worth the loss in food.
I always unplug my refrigerator after emptying it and leaving for longer than a month but I leave my deep freezer plugged in.