Correction on your model:

ET21NKXGW02
8th character = G
10th character = 0 (zero)

The evaporator drain port is typically at the back inside the top of the fresh food section. Previous design had the temp control panel at the rear, the drain port was behind the panel. Your unit has the controls at the front, I'm not familiar with access to the drain port but it must be back there somewhere ... either exposed or (more likely) behind a concealing panel.