QuickBooks Online can import CSV files that use either a 3-column or 4-column format, sbghostine.
You can only include the Invoice number, Customer's name, Invoice date, Due date, and Item amount in your CSV file. You can open this article and check out the sample CSV formats that can be imported to QBO: How to import bank transactions using Excel CSV files.
You can also get back here and add a reply below if you have follow-up questions.