You can replace the insects with 3d models

The easiest way to do it - replace art in existing enemies prefab: just go inside any enemy-prefab and
replace child object "planeUV" with your 3d-object.
For example (please also check attached screenshot):
1) In project window go to folder "Pizza_Defense\_Prefabs\_Insects\" and drag any enemy-prefab to
Hierarchy window.
2) In Hierarchy window - expand object to get access to child object named "planeUV" ... and delete (or
disable) it
3) Put any 3D model (prefab) instead of deleted "planeUV"
4) Select parent object (enemy-prefab) and put proper materials(related to new 3D object) to "EnemySkins"
and "DeadSkins" lists of Enemy script/component
5) Press "Apply" in Inspector window:

6) You can delete (or disable) the object/prefab from Hierarchy.