I am trying to compute the volume of a cell(the shape is hexagon prism but sometimes can be more than hexagon or less than hexagon) so I am trying to find a theorem that I can use to calculate the volume using the sides. I found this gauss theorem but in my case I do not know how to find the field vector(F). So is there any way to find the field vector? Moreover, in my case I do not know how to set the boundaries but I know the coordinates.
Also I am not pretty sure if there is any better theorem than works for me better.