Dimentional struct matrix

I'm trying to make a 3dimentional struct matrix. I think i have created the struct matrix, but im drawing a blank on how to fill it or get values from the struct matrix. I would like to access both Hvalue and Movementcost from f.eks matrixvalues[2,1,0] I have seen some examples where they fill it with information using something like

 t[, ,] array3D= new int[,,]{{1,2,3},{4,5,6}}

but seing as this "struct array matrix" will be pretty big it would be a little inconvenient

 public struct matrixvalues
 {
     public int Hvalue;
     public int Movementcost;
 
 };
 public class Pathing : MonoBehaviour {
 
 
 
       void HValue()
     {
         matrixvalues[, ,] matrix = new matrixvalues[7, 6, 0];
         // access or set Hvalue and Movementcost to matrixvalues[1,1,0] // using [1,1,0]as an example
     }