Answer:
SI unit of k (spring constant) = N/m
Step-by-step explanation:
We have expression for force in a spring extended by x m given by
 F = kx
Where k is the spring constant value.
Taking units on both sides
 Unit of F = Unit of k x Unit of x
 N = Unit of k x m
 Unit of k = N/m
SI unit of k (spring constant) = N/m