You mean unique IP's you've purchased, right?
You can find your usage of unique IP's in a couple of spots. The easiest is probably in "Billing>Manage Account" where at the bottom, you'll see a section labeled "Unique IP Addresses" and it will have "N used, M provided on this account" and also have a list of domains for which you've purchased unique IP addresses.
You can also probably find some information over in "Domains>Manage Domains". That's where you add a unique IP for your domain so I'd guess that you'd also be able to see which of your domains has a unique IP assigned to it. I haven't purchased a unique IP so I can't point you to exactly where it lists it over in this area.
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