First of all, hello
Now, let me understand your question, you have a 2D array, you want to populate it by calling 3 functions? this shouldn't be a problem, make 3 functions that receives a 2D dimensional array as parameter:
Look that I'm just passing the  - you cannot do something like . You can pass it in other ways, like in pointers. Now, from that function make whatever you want with this array, all changes you'll make there, it will affect in the array automatic.
void myFunc1 (int arr);