got it to work. I wasn't able to get the command working with the -ManagementPackName parameter and used the -ManagementPack parameter instead. My command is posted below.
Add-SCSMEnumeration -Parent (Get-SCSMEnumeration -Id "66b02881-ba7a-00ee-8859-b3a6fc8d4a24") -ManagementPack ((Get-SCSMEnumeration -Id "66b02881-ba7a-00ee-8859-b3a6fc8d4a24").GetManagementPack()) -DisplayName "TestRegion1Add" -Name TestRegion1Add.Enum -Ordinal 80