The safest way to do this and the way I normally do it when doing upgrades is this.
Install version 7 into it's own directory. Run the import and verify that everything is working as intended.
Backup or rename the original directory that had the old ubb.threads/classic files and then move the entire version 7 installation into the original directory.
Manually edit the config file to and change any paths necessary.
It's a bit of work, but that way your original is untouched while doing the install/upgrade. And you have all of the original files if needed for some reason.
