Father's Day surprise

Hello ladies, I have been married for two years and am expecting my first baby! my husband and I could not be happier😁 so Father's Day is coming up and long story short I want to change my last name to my husbands as a surprise. What all do I need and where do I go? The reason I didn't do it when we first got married is because we where traveling out of the country and they recommended I wait because of my passport... I know it's not pregnancy related but just thought it would be a great surprise😇