CacheRefresher GUID Value

Hi,

I'm trying to troubleshoot an issue and attempting to use Postman to call CacheRefresher and RefreshByID with the right parameters. I can't work out what to put for the uniqueIdentifier parameter, is it something that is an internal value or is it something I should be able to work out from the database or find out by another web call?

Version: Umbraco 6.2.5

Many thanks, Anne