How do I locate somebody's new employer to reestablish garnishment or who they bank with

You are responsible to locate them yourself... by whatever means you can find the info. Then you take the garnishment order to their HR department and make the request.

You also want to make sure the garnishment order is kept active... as they do periodically need renewed.

I cannot find their new employer or where they are banking do you have any suggestions

Hire a private detective. Go back to court and get an order if discovery.