Conditionally Sorting 3D Arrays

I'm making an RPG game with an unlockable slot based inventory system. At Level 1 there are 8 slots available, at Level 5 there are 16.

In my GameData array (which controls all the player modified variables for save files) I store the inventory data in the Z axis, specifically (0,3,1-16). (0,3,0) is where I store the player's currency variable.

Each slot, 1-16, holds an ID number that corresponds with an item from a different array, ItemDB. If the ID is >=0, then the item slot is filled with an item. If the ID is -1, the item slot is empty. If the ID is -2, the item slot is locked and needs an upgrade to be unlocked.

How do I auto-sort these items in a 3D array for just that small Z-axis segment from ItemID to Empty to Locked? I found some good examples for a 1D array, but nothing for a 3D array. Basically, this:

0,3,1  : 12
0,3,2  :  8
0,3,3  : -1
0,3,4  :  3
0,3,5  : -1
0,3,6  :  3
0,3,7  :  5
0,3,8  : -1
0,3,9  : -2
0,3,10 : -2
0,3,11 : -2
0,3,12 : -2
0,3,13 : -2
0,3,14 : -2
0,3,15 : -2
0,3,16 : -2

0,3,1  :  3
0,3,2  :  3
0,3,3  :  5
0,3,4  :  8
0,3,5  : 12
0,3,6  : -1
0,3,7  : -1
0,3,8  : -1
0,3,9  : -2
0,3,10 : -2
0,3,11 : -2
0,3,12 : -2
0,3,13 : -2
0,3,14 : -2
0,3,15 : -2
0,3,16 : -2

the indices for x and y don't change, so just use the examples you found and simply replace everything that refers to a complete array with the values valid for your z-axis.

For example:

For each element => replace with a for loop ranging from 1 to 16

array size => replace by number 16

arrayat(x) => replace with arrayat (0, 3, x)

etc.

Took a little finagling but it works pretty great now. Boy do I feel sheepish. Thanks Tulamide!