The defrost thermostat is going to be behind the rear panel in the freezer and on top of the evaporator there's no picture but you can talk to Danby parts dealers I'm posting a link below to the page that is related to your refrigerator and its parts it come in helpful
Danby DFF092C1WDB Refrigerator 9 20 Cu Ft

Appliance 911 Sea Breeze
If you have any other questions please let me know I'll try to answer them for you. The people that sell the parts call this a defrost protector just for your information