When using Horizon View Instant Clones several objects are created in your vCenter Inventory that are used to assemble the instant clone virtual machines. If you want to find the relationships between those objects then you can read about that in another article on this website here.
The objects that are created for instant clones are protected in your inventory. The cp-template and cp-replica objects can not be removed from the inventory or from disk. The cp-parent machines are always powered on and are protected from power-operations and migrations.
When necessary the protection can be removed and the objects can be deleted, but be careful because once the protection has been removed you could also delete objects that are still needed.
This utility is available on every VMware Horizon Connection Server in C:\Program Files\VMware\VMware View\Server\tools\bin. The documentation for this tool is available here. It can be used to delete any unnecessary objects or to unprotect the objects but it also has a simple list-function. The output in the image below shows four master virtual machines (or Golden Images as you can also call them) that show their relationship with the templates, replicas and parent machines.
This output doesn't directly tell you for which Desktop Pool these are being used but you can probably tell from the used master virtual machines for which pool you have used them.
The tool has an unprotect and a delete option. With both these commands there is a -all option that would unprotect or delete all objects. That might not be what you want to do so another options is to add the --index parameter that selectively removes a set of objects.
In the two images below you see the use of parameter --index 1 (This is the number from the list command.)
unprotect --index 1
After unprotecting the objects you can manage them in the vSphere Client.
It is also possible to delete the objects. There's no need to first unprotect them, the delete command will first unprotect and then delete the objects, as you can see in the image blow.
delete --index 1