Answer:
  v₀ = 50.46 m / s
Explanation:
This is a projectile launch exercise where the scope is given by
     R = v₀² sin 2 θ / g
Let's clear the initial speed
    v₀ = √(G R / sin 2θ )
Let's reduce the distance
     R = 0.3 km (1000m / 1km)
     R = 300 m
Let's calculate
     v₀ = √ (9.8 300 / sin2 π / 6)
Let's calculate the breast in radians
    sin π / 3 = 0.8660
    v₀ = √ (2546.11)
    v₀ = 50.46 m / s