If you already have your 10x10x10 array and it is of some different numerical class (i.e. not a cell array, structure, table, etc.)
originalArray = uint8([1,2,4,7]);
whos originalArray
then you can do
dblArray = double(originalArray);
whos dblArray
See? It's now a double.
What are you starting with? Nothing or an existing array?