You're on the right track! Now that you have drawn a right triangle with the hypotenuse as the segment from Joe's home to the Park, we can use Pythagorean Theorem to solve for the hypotenuse.
Pythagorean Theorem = a squared + b squared = c squared
A and B are the legs, and C is the hypotenuse. We can find the legs be calculating how many units they are.
2 - (-1) = 3
3 - 1 = 2
Pythagorean Theorem = 3 squared + 2 squared = c squared
= 9 + 4 = c squared
= 13 = c squared
= [tex] \sqrt{13} [/tex] = c
The square root of 13 is around 3.6, so Joe's house is approximately 3.6 miles away from the park.