Square root of a number is the number that multiplies by itself to result in, in this case, 14. The number is irrational, often, though here is close to 3.74, according to the calculator. Many, though not all, courses recommend calculators for determining square roots, as the mathematical process is quite complex and often not taught. Try this if your course allows, and if not, wow that's a tough course.
The square root of 14 is between the square root of 9 and the square root of 16, so it is between 3 and 4. However, since 14 is much closer to 16 than it is to 9, the square root of 14 will also be closer to 4 than 3. So, a pretty accurate estimation would be 3.74.