Hello Musyoka Kilonzo,
Thank you for contacting the Microsoft Q&A Community.
From my understanding, you would like to know how to allow your Power automate access to your key vault via private network access.
To be able to resolve this, you need to know which IP address range the Power automate connects from. You might want to get that by looking through this link
https://learn.microsoft.com/en-us/power-platform/admin/online-requirements
However, it might not be that easy to get this IP address. As a workaround, enable Azure key vault logging, set the network to public disabled, and try to initiate the connection. After some hours, you should have a log within the storage account to see from which network the power automate is trying to authenticate.
Follow the link below to see the steps on how to create key vault logging.
https://learn.microsoft.com/en-us/azure/key-vault/general/howto-logging?tabs=azure-cli
Let me know if further assistance is required.
Babafemi