I Fusion, go to lhcb > layerb

The top copy (orig) is made by many extrusions, which are
separate bodies, which makes splitting into 3x3 impossible.

The second layer (combined) combines all bodies into one.

The third layer (split) splits into 3x3 sections. Bodies are
exported from there (save as mesh).

The parameters can be set to correspont to A,B,C,D.