Hi Pollymaye,
Welcome to QuickBooks Community! I can understand the concern with moving your data to QuickBooks Online and the need to get back to business as soon as possible. I'm glad to hear that you were able to maintain a backup of your Sage 50 files. Intuit doesn't offer technical support for creating or importing IIF files. For additional assistance, I suggest reaching out to an accounting professional. If you don't have one, we can help you locate a ProAdvisor in your local area.
Please feel free to reach back out if you have any other questions. We'd be happy to assist!