You are right! Was too hasty!. 3^3 x 5^3, 3^3 x 5^6, 3^3 x 5^9, 3^6 x 5^3, 3^6 x 5^6, 3^6 x 5^9=
3375, 421875, 52734375, 91125, 11390625, 1423828125
I think I got them all: 5 + 6 = 11 perfect cubes? Since you know what to do, you can check them and see if I missed any.