Your problem is compounded because you are trying to jump over two hoops at once. The first one is the transition from QP 3.x to QP 4. The other obstacle is transition from IAR EWAVR 4.x to 5.x.
Perhaps it would be easier to jump only one hoop at a time. Maybe you can keep using IAR EWAVR 4.x at first and focus on upgrading to QP 4. I'd take the old workspace and project file, but replace all sources in the application directory with new versions. Also, you'd need to upgrade the port itself. Please take a look at the port for WinAVR (GNU).
The official QP port to IAR will be of course for the latest IAR EWAVR 5.x. I'm a little swamped at the moment, however, so that port will need to wait a bit. One of the reasons for delay is that my license for the full-verion IAR AVR compiler has expired, and the 4KB-limited KickStart version is too small to show Q-Spy and other features.