You can't, I assume... The r10 version uses the commercial file format (with a watermark), while the r9 version used a non-commercial format.
Maybe a reseller can help you with it?
Or a UNIVERSITY version?
--- stefan boeykens --- bim-expert-architect-engineer-musician ---
Archicad28/Revit2024/Rhino8/Solibri/Zoom
MBP2023:14"M2MAX/Sequoia+Win11
Archicad-user since 1998
my Archicad Book