I understand you hoped to import an IIF file into QuickBooks Online,
jake32. Let me share some insights about this matter.
Importing IIF files isn't supported in QuickBooks Online. QBO uses a different file format, such as CSV file, Quicken (QFX), QuickBooks Online (.QBO), or Microsoft Money (OFX).
I understand that this may be different from the outcome you were expecting. Still, the only alternative solution or option that may be available is to consider using third-party tools or services to convert it before importing it into QuickBooks Online. To be guided on what app to use and integrate it into QBO, go to the Apps menu and browse available applications that suit your business needs.

Furthermore, check out the Common questions about importing data to QuickBooks Online that provide additional details and answers.
I'll keep this thread available if you have more questions or need assistance importing files or other relevant concerns. I'm here to assist you.