In AVD unable to change pool for vm

Hi C Rajesh,
Based on your query,
Once you have created a personal host pool in Azure Virtual Desktop, you can't change it to a pooled host pool directly. Azure doesn't support switching the host pool type after it's been set up. As per below documentation & SS

https://learn.microsoft.com/en-us/azure/virtual-desktop/faq#can-i-change-from-pooled-to-personal-host-pools-

Instead, you'll need to create a new pooled host pool and manually migrate your resources, like virtual machines and users, from the personal host pool to the new pooled one. While this process involves setting up a new host pool and reconfiguring your environment, it's a common approach when transitioning between different host pool types

You can add session hosts to Azure Virtual Desktop either by creating new VMs directly in the portal or by manually registering existing VMs. The portal method handles setup automatically when you add session hosts to a host pool.

Please refer the below documentation for more information
Create and register session hosts

If you're using existing VMs, you need to install the AVD Agent and Boot Loader manually and use a registration key from the host pool. This process links the VM to the host pool so users can connect through AVD.

Please refer the below documentation for more information
Register session hosts to a host pool

If you need any other information, please let me know just ping me in comment will help as always you need