Call and ask Intuit Data Service to convert it
https://quickbooks.intuit.com/learn-support/en-ca/getting-started/import-from-quickbooks-desktop-and...
Make sure you have open your QBO account
https://quickbooks.grsm.io/Canada
Another option, consider purchasing a 3rd party conversion service. They may convert your data file to QB Desktop file, then you may self migrate it to QB Online. You may keep that QB Desktop data file for archive.
