Add a treadmill and refrigerator to the wall outlet in my garage without tripping any circuit breakers?
As a renter, your &quot;work&quot; can only consist of trying to track down what the actual relationship of circuits to locations is (see if there's another spot that &quot;looks like&quot; it could have had a washer/dryer, for instance) and trying the devices you want to run on the outlets you want to run them on to see if a breaker trips, or not - given that modern refrigerators are usually small loads (mine does 50-60W unless it's defrosting at 200W) your main likely issue with overloading would be don't wash and dry and treadmill at the same time.
We have some previous questions and answers about tracking down circuits. Labelling is often outdated or wrong - just be systematic and make a note of what breaker affects each device location.
Any electrical work on a rental has to be done by a licensed electrician (as others already commented.)