It depends on the size or length of the swimming pool.
If you're swimming in a 50 yard or 50 meter swimming pool it will take you around 30 laps of swimming to cover a mile of swimming.
In a 25 yard or 25 meter swimming pool it will take you 60 laps to cover a mile of swimming in that swimming pool.
Being able to swim a mile is a great thing if you're able to accomplish it and it will give you great exercise.
To swim one mile it would take around 45 minutes of swimming including your breaks while swimming the mile.