Hi,
is it an option to upgrade old server to the last version first? It should simplify migration. Alternatively, you can try to upgrade export file directly (although it may fail) - it is essentially an SQLite database, so you can set your netxmsd.conf to be like this:
DBDriver = sqlite.ddr
DBName = /path/to/export/file
and run nxdbmgr upgrade. Then revert netxmsd.conf to correct settings and try import again.
Best regards,
Victor