We provide the following files:
A - a set of Binaries zip files: ExportDiagramGeometry_Binaries, ImportDiagramGeometry_exe_Binaries and ImportDiagramGeometry_ProAddIn_Binaries
B - a PDF document, ExportImportDiagramGeometryCommands_HowToUse.pdf
C - the ExportImportDiagramGeometryCommands_SourceCodeFiles zip file

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A - About the set of Binaries zip files
From the ExportDiagramGeometry_Binaries zip file, you get an ExportDiagramGeometry folder referencing two subfolders; ExportDiagramGeometry\10.6 and ExportDiagramGeometry\10.8.2. Those correspond to the ExportDiagramGeometry standalone .exe commands to copy and use on your ArcGIS Desktop client to export the geometry of each schematic feature present in your schematic diagrams to JSON files.
With the ImportDiagramGeometry_exe_Binaries zip file, you end with the ImportDiagramGeometry_exe folder that comes with three subfolders; ImportDiagramGeometry_exe\2.6, ImportDiagramGeometry_exe\2.9 and ImportDiagramGeometry_exe\3.1. Those are the standalone .exe commands to copy and use on your ArcGIS Pro client to import the geometries exported in the resulting JSON files above onto the diagram features in your new network diagrams.
When you unzip the ImportDiagramGeometry_ProAddIn_Binaries zip file, you get the ImportDiagramGeometry_addin folder and its three subfolders; ImportDiagramGeometry_addin\2.6, ImportDiagramGeometry_addin\2.9 and ImportDiagramGeometry_addin\3.1. Those are the ArcGIS Pro add-in command you must copy and install on your ArcGIS Pro client to geometries exported in the resulting JSON files above onto the diagram features in your new network diagrams.
NOTE: Please copy, install and use the .exe command/Pro add-in that is compatible with the ArcGIS Desktop/ArGIS Pro version installed on your clients.

B- To know more about how to run these sample standalone .exe and add-in commands, read the ExportImportDiagramGeometryCommands_HowToUse PDF document.

C - About the ExportImportDiagramGeometryCommands_SourceCodeFiles zip file
This file regroups the source code files related to the .exe standalone and add-in commands provided in the Binaries zip files. 
After you unzip the ExportImportDiagramGeometryCommands_SourceCodeFiles file, you get a SourceCodeFiles folder with a hierachy of subfolders:
- ExportDiagramGeometry - related to the ExportDiagramGeometry standalone .exe command source code files (developed using ArcObjects API Reference for .NET). This folder references two subfolders; ExportDiagramGeometry\10.6 and ExportDiagramGeometry\10.8.2
- ImportDiagramGeometry_exe - related to the ImportDiagramGeometry standalone .exe command source code files (developed using ArcGIS Pro SDK for .NET). This folder comes with three subfolders; ImportDiagramGeometry_exe\2.6, ImportDiagramGeometry_exe\2.9 and ImportDiagramGeometry_exe\3.1
- ImportDiagramGeometry_addin - related to the ImportDiagramGeometry add-in Pro command source code files (developed using ArcGIS Pro SDK for .NET). This folder comes with three subfolders; ImportDiagramGeometry_addin\2.6, ImportDiagramGeometry_addin\2.9 and ImportDiagramGeometry_addin\3.1

NOTE: Please be advised that these binaries and source code files are provided as code samples without any code maintenance.

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RECOMMENDATION: To understand more about the differences between schematic diagrams and network diagrams and get guidance to help you in porting your ArcGIS Desktop schematic diagrams to ArcGIS Pro network diagrams, read the following ArcGIS blog: https://www.esri.com/arcgis-blog/products/utility-network/data-management/network-diagram-consistency-states/