How do you work out the square root

Example: you basically take two numbers that would multiply to the original number. Then with those numbers you find if they are divisible by any number that would have two of the same like 16 would be 4 and 4 or if you had 8 it would be 4 and 2 so you go to the 4 which it 2 and 2 the you would take the number that wouldn’t break down and use it so like in the picture above