If you want the first three of the original 13 states, they are:
Delaware (December 7, 1787)
Pennsylvania December 12, 1787
New Jersey December 18, 1787
These are the first colonies to become states. So all of this started with Delaware. I’ll just say that again to let it sink in – Delaware – aka the Blue Hen State, the Diamond State, the First State.
In the US immigration test, you are only asked for three of the original thirteen states, so any three will do. The list above is simply the first three, which became states in 1787.