How to Reverse Calc Pixels measurements?

[CNBA3]

What I am trying to find here is how you can calc how much distance is covered in a pixel on an image when you have gotten the values from below, this is from using the mass of a ship and the density which is steel to find the volume, and then converted with ratio calculation how many pixels are equal to said volume:

1. Mass = 300,000 tons
2. Density of steel = 7.85 g/cm^3
3. Volume = 2115661506.51 in^3 = 203103504624.96 voxels/pixels cubic
4. Surface Area = 9888157 in^2 = 949263072 pixels square
5. 1 in = 96 pixels
6. 0.0104 in = 1 pixel

So what I am trying to do now is find what is the best way to get the reverse for that with the image of a ship at a distance to get 1 pixel to equal a greater value for scaling purposes.