Bank statements are provided by your financial institution. You can ask your banks for a file of your bank statement and use it to import to QuickBooks Online. If you mean by something else, I'm here to provide more information.
In QuickBooks Online, connecting your bank to QBO has limitations on how far back they can retrieve transactions. Some banks only provide the last 90 or 60 days. However, there's a workaround to unlock this limit and access older bank transactions based on your bank statement.