Idon't understand the formula and how to find the 'n' in y=p(1+r/n)^nt
"^" means 'to the power of' right?
needs to find n

N in the formula
.. y = P(1 +r/n)^(nt)
is the number of compounding periods in a year (when the interest rate r is an annual rate).

Your problem statement makes no mention of compounding. It appears as though you are to assume interest is compounded annually, meaning n=1.
.. y = 500(1 +.06)^10 ≈ 500*1.790848 ≈ 895.42

The value of the investment after 10 years is $895.42.

The answer to your question is the last one