The drop down control at the bottom of the wizard gives you options on how to proceed.
Update Now will convert the old job into the new format.
Upgrade later (maybe) will allow you to press continue to work with the old crewing – but each time you come back to the job you will be prompted to upgrade again.
Upgrade Never will leave the Crewing in the old style and you will not be prompted to upgrade in the future.
Once you have chosen your option – press the ‘Continue’ button to confirm