P - Po(1 + r/n)nt
P = $10,000
r = 6.5%
n = 12
t = 216MO
You did not write the formula correctly. It should be
P = Po(1 + r/n)^nt,
n is the number of compoundings per year (12 in this case) and t is the number of years, NOT months. t = 18 here.
The $10,000 you have been given is the initial principal Po, NOT P.
Now that you have the formula, use it.
P (after 18 years) = $32,118.36