Hi Joshua,
Have you tried the Puzzle Designer app?
If you draw a rectangle with your desired dimensions and then select it and open the puzzle designer, you’ll be able to adjust how many rows and columns you want in the puzzle.
The puzzle is normally used to construct a design when the pieces are assembled. Since you don’t want a design, you just want the pieces, after you import the puzzle, choose “Edit / Select By Cut Type / Fill” to delete the fill shapes and just leave the piece outlines.