Fast alternative to objects

Question

Im writing a cube voxel like game and wanting to get more performance. Currently I create the cubes like this

for (size_t i = 0; i < 20000; i++)
    {
        objects* cube = new objects;
        cube->position.x = 
         ----------
        cubes.push_back(cube);

    }

and then I loop through all the objects to change their positions and stuff and render them too using

for (auto& cube : cubes)
{
    //change cubes position stuff etc
}

Problem is once I spawn in 100,000 cubes my game starts lagging. I did a similar thing in the past where I used java and I was able to spawn in 2,000,000 and got around 5fps but I lost the code but I know my current code can be optimised.

So I gave this much thought and I thought of this instead of using objects

float world[maxworldlength][maxworldlength][cubesperchunk][cubesperchunk][cubesperchunkdeph][x][y][z];

where here I can put all my objects in my world in a single list and can easily access any property without loops etc and maybe its faster for cpu since data all together. But I gave this some more thought and I thought about how much ram this would use. after some simple math ((32 * 10) * (32 * 10) * (32 * 16) * (32 * 16) * (32 * 50) * (32 * 50)) / 1000000000. I found that the array would use over 68719476 GB of ram. So I had to scrap that idea.

Anyone know how I can store mass amount of objects with small performance hit. Thanks for any help/.