Question on tickets after deleting a template

[Deenie Petros]

We have JIRA cloud and on our service project board there are a lot of template options. We're looking to consolidate and create 3 standard templates and delete the old ones.  Optimally, we'd like to just hide them or mark them not in use but that seems to not be an option.  My concern is if we delete them, what happens to the thousands of closed tickets?  Those that are open, we can move to a different type, however there are way too many closed for that.  Also, we want to make sure we don't lose any of that historical information.  

[Mikael Sandberg]

If you remove a request type you will get a warning if you have work items that are associated with that request type. If you go ahead and delete the request type the work items that were associated with it will no longer be visible from the Portal, but the data will still be retained.