You need to break up the velocity into horizontal and vertical components. Also remember that the vertical component will be affected by gravity.

a. In order to calculate the range, you need to know when the projectile hits the ground, using the vertical component of position. Then substitute this value for t into the equation for the horizontal component of position.

b. Find out when the vertical component of velocity is equal to zero and substitute this value for t into the equation for the vertical component of position.

c. Combine the vertical and horizontal components of velocity for the t you calculated in part a. Or by symmetry, determine that the answer is 500 m/s.