Hi Adam,
Get-UcsIpPool will give you total IP Pools and expression after that will print Name of IP pool and available IP's. (Size - Assigned)
PS C:\> Get-UcsIpPool | %{$_.Name + " " + ($_.Size - $_.Assigned)}
ext-mgmt 0
iscsi-initiator-pool 5
Let us know if above works for you.
Thank you,
Nitin