Sterilize a glass jar and dry thoroughly.
Pour the sweetened condensed milk into the prepared jar and seal the lid.
Place the jar onto the trivet inside of the Instant Pot and carefully fill the insert with water until it fills halfway between the milk and rim of the jar (the water should be about an inch below the rim).
Close the lid on the instant pot and turn the valve to the sealing position. Cook on high manual pressure for 35 minutes.
Quick release the pressure after cooking and remove the jar from the water with a strong pair of tongs. Allow the dulce de leche to cool completely before opening.