A few days ago, we talked about that backing up your certificates is an important part of your SQL Server recovery strategy. A recovery strategy cannot be complete without a way to execute a restore. Yet, SQL Server does not have a RESTORE CERTIFICATE statement prepaidgiftbalance.com
As comstock posted, you'll need a copy of your cetificate, if you don't have a copy you should export the one that is installed on the server. Note than a migration is diffferent than an upgrade. Migration usually means you move to another server while an upgrade usually is done on the same server.