Hi there,
Thanks for reaching out with your question. I'm happy to hear you've joined the QuickBooks Online family! Using a cloud-based program will give you a lot more flexibility in your bookkeeping. Migrating from QuickBooks Desktop to QuickBooks Online is a big step, and it's important that you're aware of how the process works.
There's a few things that don't convert when you transfer over your data. Bills and Bill Payments is one of those features. To see a complete list of which parts won't be converted, take a look at this helpful Community article: What data doesn't convert from QuickBooks Desktop to QuickBooks Online?
In order to add the Bills and Bill Payments back into your books, you'll simply do this manually in your new QuickBooks Online account and select the transaction's original date. To see a list of steps on how to enter and pay bills in QuickBooks Online, take a look at this article:How to enter and pay bills.
Easy as that! Now you'll be able to get your new account up to speed. Please let me know if you have any other questions.
Have an awesome day!