I’ve been off this site for a bit & it’s been quite awhile since you posted your question… but just in case you hadn’t found a solution; I’m assuming your new environment is in the OS/390 series.
Try IBM’s site for the COBOL Family. Under the Support, library, etc., categories you can find great material. The Programming Guide is one of my personal favorites and is a free download (pdf file).
If no coding changes are being made the only differences you might encounter that can cause errors is with the compile options. Solutions for this can also be found at the IBM site.