Crack The Code

The chef is an agent and is trying to enter into a facility through a secret door. To enter through the secret door, he needs to enter a code. The code is a substring of a string which is formed by concatenating the squares of all the primes in ascending order (i.e “492549121…..”). Chef finds 2 numbers ($N$ and $K$) as a hint. $N$ is the index and $K$ is the length of the substring that is to be u