The esophagus is simple to find on diagrams, usually shown as a long tube leading from the mouth to the stomach. On preserved specimens the esophagus can be challenging to locate. It is soft tissue that lies next to the trachea (identifiable by the cartilage rings) and can be mistaken for muscle or connective tissue.
If you locate the esophagus, try making a small opening in it and inserting a blunt probe. The blunt probe can be pushed all the way into the stomach and reveal the location of the esophageal hiatus (the opening in the diaphragm where the esophagus passes through.)