We have JasperReport server v 3.0 in our production which were never upgraded. Finally we have decided to upgrade to latest and according to documentation I have to follow this upgrade path 3.0 -> 3.5 -> 3.7 ->4.7 ->5.6.
The problem is I cannot find installation packages for 3.5 & 3.7 anywhere because its support is ended. Can anyone please help me in finding packages. It will be very helpfull.
It's possible to build them from sources. If you don't have too many reports, you can try opening reports with Jaspersoft Studio and re-saving them on to the new 5.6.1 server.
This isn't directly related to your current issue but iReport is going to reach end of life next year too. It's better to switch to Jaspersoft Studio now to avoid similar situation.