I'm having two release version as 1.5 and other new is release v2.0 in jira. Till now I was having 16 sprints in Release 1.5 Now I want to have new sprints under release 2.0.
How can I do that? Is there something I'm missing or going in wrong direction?
Sprints are for ongoing agile development, where "releases" are related to more basic kanban workflows where you have a WIP (work in progress) workflow and just release active "sprints" into a release version.
When you use a Kanban software development project, it's not following the scrum agile project workflow model so it replaces the "sprint" with releases. Once you fill your max WIP (say 10 tasks), once complete, you release the completed work into a release version. This differs from a sprint because it's based off how much work your team is allowed. Sprints, part of the scrum/agile project type in JIRA are run against date ranges. Any uncompleted work in a sprint is moved to the next sprint.
If you're talking about these releases, what you can do is change the project type you're using and "versions" instead of releases.
Versions track independently of sprints and allow you to have a 1.5 and 2.0 version that can be tracked against multiple sprints. Sorry for my previous answer. Several products intermix version and release.