369.38 km
speed,x = 2.07cos(28.8°) = 1.81 km/s
speed,y = 2.07sin(28.8°) = 1.00 km/s
v_{f}=v_{0} +a * t
0 = 1000 - 9.8 * t
9.8 * t = 1000
t = 102.04 s
After reaching the highest point the shell takes the same time to reach the ground where it was fired, so the total time it flies is 102.04* 2 = 204.08 s
d = 1.81 km/s * 204.08 s (I used the speed in km/s because the answer needs to be in km)
d = 369.38 km