Welcome to the Community, info1367!
QuickBooks Online is the perfect accounting program for managing your small business' books. Keeping track of invoices and ensuring an accurate numbering system is important, so I'm glad you reached out for support. Let me explain how you can continue with your existing numbering scheme for invoices without having to start over from 0.
When creating a new invoice, you'll notice the Invoice no. field to the right, beneath the balance due. This field is actually editable, so you have the ability to erase the number that QuickBooks populates and enter your own. It would make sense that the next invoice you create has number 10,001, so you can enter that number into the field. After that, QuickBooks will automatically populate the correct next number on every invoice you enter. The following one will be 10,002, then 10,003, and so on.
Let me know if you have any follow-up questions. I'm here to help!