First calculate the time required. At constant deceleration -5g= -49 m/s^2, your speed will go from 1000 km/s= 1000000 m/s to 0 in 1000000/49= 20408 s.
During that time you will have gone a distance of (49/2)(20408)^2= 10204081633 m= 10204081.633 km.