If you want to backup your UCC certificate along with corresponding private key, Export the UCC certificate using Export-ExchangeCertificate cmdlet by the following command.
Export-ExchangeCertificate -Thumbprint -BinaryEncoded:$true -Path c:\certificates\export.pfx -Password:(Get-Credential).password
To Import the certificate, use the following command.
Import-ExchangeCertificate -Path c:\certificates\export.pfx -Password:(Get-Credential).password
If you want to get the Thumprint of your installed certificate, Open the Exchange Management Shell [ START -> Programs -> Microsoft Exchange Server 2007 -> Exchange Management Shell ] and type the following command