What is your server OS?
Linux or Windows
linux ubuntu 18.04
one thing to note. if it is ok to go right from ubb.classic 6.7.3 to ubb.threads 7.7.3, the classic_import.php file in the ubbclassic_6_7_import needs a slight tweak. on line 48, you need to change this line
from:
require_once( "../libs/mysql.inc.php" );
to:
require_once( "../libs/mysqli.inc.php" );
I decided to just go ahead with the import since it's only a test currently...I'll report back once it's finished.