Upgrading to Jira 6.4 and Service desk 3.0.0

[Jabir NP]

This question is in reference to Atlassian Documentation: JIRA Service Desk 3.0.x release notes

JIRA is running on 5.2 and Service desk  1.1.1, We are planning to upgrade to JIRA 6.4 and Service Desk 3.0.0. Please let me know if there is any known issue and guide to do this activity. 

Is there any issue in data migration?

[Nic Brough -Adaptavist-]

Not going to happen.

JIRA Service Desk 3 only works on JIRA 7+, and it's now an Application rather than an add-on.  

If you stick with JIRA 6.4, then the highest Service Desk version is 2.5.9.

If you want to go to JIRA 7, then your best option is to go to the latest version of JIRA Service Desk  (The installer is a bundle of JIRA 7 Core and the JIRA Service Desk application).  See https://confluence.atlassian.com/migration/jira-7