Rearrange Hierarchical Data

I've always gotten great help here and, as I'm nearing the end of my project I tend to save the hardest parts for the end (as I always do), so I must ask for your help once more. It's as confusing as anything I've done before, so I'm going to try and explain it the best I can.

Scenario:
I input assembly information into a sheet ("Data"). This info includes part numbers and the hierarchy of how they're assembled (Part2 is a subcomponent of Part1, Part3 is a subcomponent of Part2, etc). On the sheet where I enter part info, I've created a column to enter the hierarchy, where a "1" is the top-most parent part, "2" would be a child of the "1" above it, "3" would be a child of the "2" above it, etc. This can repeat for multiple assemblies, but any number is the child of the lower number above it.

Excel_Hierarchy_Input_Example.png

This all comes around to the way we reformat the parts for another group to enter into our database. We must list the parent (on sheet "MMG_BOM") in the first column, then each child next to that parent in the second column. Which looks like so:

Excel_Hierarchy_Ouput_Example.png

There's such a weird order to it, but there's an order nonetheless. I would be more than happy to clarify anything (I've attached the file as well). I really appreciate any help.