The rest of the parts you'll need can be found on the original! I wouldn't change anything about those!
Link: https://www.printables.com/model/180488-stackable-modular-screw-box-organizer/comments/586750
Changes made:
- YELLOW - Replaced rounded posts with chamfered posts for better print quality (printing the rounded over posts with low infill can cause blemishes)
- RED - Added .4mm to the supports so the boxes inside of the drawers don't get stuck with you pull to open a drawer
- BLUE - Added rib to strengthen long, flat surfaces and, more importantly, keep the drawers from rotating and getting stuck on rear supports (back corners of drawers get crooked and hit on the rear “L” shaped supports so you had to keep them exactly straight when closing)