Export Relationships to Import to Another ItemType

Good day all.  I would like to export all of the Relationship info from one ItemType so I can import it to another ItemType.  Currently our database is configured so the Parts List (BOM) is a document and not part of the Part, both are custom ItemTypes.  I would like to be able to export the BOM information from the Parts List so I can add it to the Part (trying to bring our database closer to OOTB).  Thank you for any recommendations that you can provide.