Hi @TikaAdhikari ,
Here are some resources that I hope you find helpful.
Utility network FAQs:
Utility network upgrade history:
Utility network compatibility:
Blog post about "What's New for ArcGIS Utility Network in ArcGIS Pro 2.7":
The documentation for ArcGIS Pro 2.7 is currently available, but any specific documentation for ArcGIS Enterprise 10.9 is not yet publicly available.
Keep a lookout for ArcGIS Pro 2.8 and ArcGIS Enterprise 10.9 web help to be available in the near future (estimated mid Q2 of this year).
Once the web help is updated, this page will reflect 2.8 changes
Once ArcGIS Enterprise is live, this page will reflect 10.9 changes