There are two ways you can find out the length: Draw a right triangle with the two ordered pairs and find the hypotenuse of it using Pythagorean theorem or use the distance formula. I'm going to use the latter. 
Distance formula = 
 where (X1, Y1) is the first ordered pair listed and (X2, Y2) is the second.
 where (X1, Y1) is the first ordered pair listed and (X2, Y2) is the second. 
Now, just plug in and solve. 
Distance = 

Your distance between the two points is √205 units or ≈ 14.32 units