If you want to get n-value, based on p-value, then you can visit
Sage Cell Server and use this code:
p = 0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffef9
P = GF(p)
aP = P(0x0)
bP = P(0x7)
Secp256k1 = EllipticCurve(P, (aP, bP))
print(hex(Secp256k1.order()))
Then, you will see 0xffffffffffffffffffffffffffffffff9d70b40e72725ad652cd62c55808d873 as a result.