I am assuming k starts at 0. Python code (or pseudocode) would be this:
-------------------------------
S = 0
count_term = 0
k = 0
while S <= 2000: S = S + 3*k**2
count_term = count_term + 1 k = k + 1
print(count_term)
-------------------------------
It will print 14
If k should start at other number then just replace number at third line and execute it.