Hi Friend,
While you are planning to migrate an old controller to a new model you have consider the following points,
1. WLAN configurations
2. L2 and L3 configurations
3. Local database
4. License
As a good and successful practice,
1. take the flash backup from the old controller, use the command " backup flash"
this take care of first 3 requirements.
2. boot the new controller and factory rest the controller, use the command " write erase all"
3. After rebooting the controller, copy the backup file in to the flash
note the file name must be "flashbackup.tar.gz"
4. restore the flash backup, use the command " restore flash "
5. Now configure the L2 and L3 interfaces accordingly ( mostly you have to work on mapping interface to the respective VLANs)
6. transfer the license.
7. reboot the controller.
for any reason if the flash is not restored, please repeat the steps 1,3 and 4
Hope got some more clarity,
Please feel free for any further query on this.