Jira does have a means to import data directly from your Trello instance. There is a short youtube clip that also explains the quick steps to do this:
This is the simplest way I am aware of to move this Trello data into Jira Server. If you don't see the Trello option in the external import, then I would be interested to learn more about your specific version of Jira.
If you're using Jira Cloud (Atlassian hosted), then that exact menu might not be available but you can still do this. In Jira Cloud, you would need to go to Cog Icon -> System -> External System Import and select the Trello import there.