too large for migration assistant
My user data is too big to move from my old Macmini to new one so I copied it to external drive. But I can't seem to get it back with migration assistant. Any other more manual methods?
Migration Assistant need a proper backup to migrate from.
The best way, is to backup the old Mac Mini using Time Machine and connect that backup to the new Mac.
Another way, is to backup the old Mac Mini with CarbonCopyCloner or SuperDuper and connect that backup to the new Mac.
The worst and least efficient way, is to skip Migration Assistant and manually move you data from whatever you have copied to the external drive.
At this point, I strongly suggest grabbing another external drive and making a Time Machine backup of the old Mac Mini and use it to migrate to your new Mac.