Mold in a fridge is not only a turnoff, but it is also a health risk. A fridge in use isn't likely to suffer from mold attack, but a fridge in storage can easily experience mold growth. Fortunately, that will only happen if you don't execute the following preventive measures:

Empty the Fridge

This seems rather obvious, but you should take everything out of your fridge if you are taking it to storage. You need the fridge to be completely dry and experience efficient air circulation, and both targets will be difficult to attain if the fridge isn't empty. Therefore, even food with long shelf lives (such as canned food) should be taken out of the fridge before storage.

Defrost the Fridge

The ice buildup in the freezer will melt in storage, and encourage mold growth if you don't take care of them. Therefore, defrost the fridge and open up its doors so that the ice buildup can melt. You can use a hard object to scrape away the ice (gently) to accelerate the process.

Clean and Dry the Fridge   

Cleaning and drying the fridge is important for two main reasons. First, it ensures that everything inside the fridge is truly removed, including bits of food that may have fallen out of their containers. Secondly, it ensures that the organic materials that might have encouraged mold growth are removed. As you know, mold thrives on moisture and organic materials.

Take out the Shelves and Open up the Doors

As you might have noticed, a common theme of preventing mold is to keep the fridge dry. Apart from drying up the fridge before storage, proper air circulation will also help keep moisture at bay. Therefore, after drying up the fridge, remove its shelves and open up its doors to encourage efficient air circulation.

Choose A Dry Storage Place                 

Lastly, choose a dry storage place where your work of cleaning up and drying the fridge won't be undone. Make sure the place doesn't leak or develop moisture issues when it rains. It doesn't have to be a climate-controlled place; any clean and dry storage place will do.

You don't need a climate-controlled storage unit for your refrigerator, but the place needs to be dry as explained above. The storage facility manager should be able to explain to you the measures in place to prevent water issues, such as flooding. Hopefully, you will find a safe and dry storage place for your fridge.