You might like to recall that the pdf of an $N(\mu, \sigma^2)$ random variable is

$$

f(x) =\frac{1}{\sqrt{2\sigma ^2}}e^{-\frac{(x-\mu)^2}{2\sigma^2}}

$$

and that the probability of a value falling between $a$ and $b$ is

$$

P(a< x< b) = \int^b_a f(y)dy

$$

Don't forget that the integral is the area under the curve between two points.

Don't forget that you can look up the cumulative probabilities for a normal distribution using tables.