Unless you provide a LOT more info, i suspect no one will be able to help you.
There is basically nothing in common between jcl and xml. . .
JCL is a Control Language used mostly on IBM mainframes of one kind or another while XML is way to create common information formats and share both the format and the data on the World Wide Web.
JCL causes things to happen - XML has no executable instructions (that i'm aware of).
If you post a very simple (small) job's JCL, and explain how this is to be "converted", we may be able to offer a suggestion.