(it is) (one's) pleasure
One was glad to do it and would do it again. A response to "thank you." A: "Thanks for picking up that package for me." B: "Oh, it was my pleasure. Happy I could help." A: "Thank you so much for helping my children, officer." B: "My pleasure, ma'am."
it’s a ˈpleasure
used after somebody thanks you for doing something to help them: ‘Thanks for the meal.’ ‘It’s a pleasure.’