To find out which Monitor is configured in which Subscription we can use the below PowerShell scripts.
Open Operations Manager PowerShell window :
1) First we need to find out the Monitor ID of the Monitor. To find out the Monitor ID execute the below command from the Operations Manager Shell.
Get-SCOMMonitor -DisplayName "My_Monitor_Name" | Format-List -Property DisplayName, Id
2) With the second PowerShell command we will retrieve the Subscription names by providing the Monitor ID.
Get-SCOMNotificationSubscription | Where-Object {$_.configuration.Criteria -like '*Type_the_Monitor_ID*'} | Format-List DisplayName
Good luck !