You will need version 10 to open a 6.5 file.
Version 12 can only open back to version 8 (8.1?).
File convertors can be downloaded here but not sure how they work if you are running a student version with a license serial number and not a WIBU key.
http://www.graphisoft.com/downloads/fileconverter.html
Barry.
One of the forum moderators.
Versions 6.5 to 27
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11