9.2.0 is a fairly old version at this point. There have been numerous defects fixed, especially around interface remapping, more resilient services such as the Reaper service being much more stable then earlier releases. Newer features such as NBAR2 application mappings. The Flow Statistics page which allows you to monitor flow rates for all Harvesters directly from the NFA web page. These are just some of the improvements over 9.2.0.
In order to upgrade to 9.3.6, being you are on 9.2.0, you would need to first update to 9.2.1, then to 9.3.3. Once on 9.3.3 you would need to migrate to a Windows 2012 server, before being able to upgrade to 9.3.6. If you cannot migrate to Windows 2012 right away, we would still recommend getting to 9.3.3 which is a very good release.
Below are some upgrade path tips and best practices:
Tech Tip: NFA 9.3.3 Upgrade Path
Handy Guide: NFA 9.3.3
Tech Tip: How can I upgrade to NFA 9.3.6?