How to migrate the data from IBM EWM to JIRA?

I agree with Ian, you should ask on JIRA forums. What you can and can not import also depends on JIRA -> ask in their forums. 

The Work Item Command Line WCL https://github.com/jazz-community/work-item-command-line can export most of the work item attributes to CSV. It can also export attachments to some extend. That does not mean you can import them in a meaningful way. It can export links, but that does not mean you can import them in a meaningful way.

You can always export as much data as you are willing to develop exporters like WCL. If you don't want to, you can only what you can export with built in tools. Import is based on the target tool capabilities. You usually loose the history and comments are hard to export as well.