How to find Values N and K given R,S and Z in ECDSA?
k and n are not values that you calculate. k is randomly generated while n is predefined by the curve parameters.

n is the order of the curve G. It is defined by the curve parameters for the secp256k1 curve which are defined here: http://www.secg.org/sec2-v2.pdf. In those parameters, n = FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141.

k is a randomly generated integer that is used only once for a signature. It is known as the nonce and acts as a source of randomness. If the same k is used to sign two different messages with the same private key, the private key will be leaked.