Hi there,
Glad to have you join the Community. I'll be happy to steer you in the right direction so you can achieve your QuickBooks goals.
In order to accomplish the goal mentioned above, I recommend looking into using a third-party apps that allows you to import sub-customers. You can search for apps on our app store www.apps.com. I suggest choosing an app that suits your business needs based on the app description/reviews.
In case you decide to manually export the data and import it into QBO, I recommend checking out the following article as it shows you how to: Import Data into QuickBooks Online.
Let me know if this info helps. I'll be a message away.