Hi there, @jeni-tan.

I'd be glad to help you get your data to QuickBooks Online.

You can use either CSV (Comma Separated Values) or XLSX (Excel file) to import information to QuickBooks Online. I can show you the steps on how to do that.

1. Go to the Settings, and select Import data under the Tools column.
2. Choose the data you'd like to bring into QuickBooks. I've added this screenshot for your additional reference: 
   

I've added this article to know more about the templates: Common questions about importing data to QuickBooks Online.

I've also added this article for your future task about managing your QuickBooks company: Get started with QuickBooks Online.

I'll be here if you need further assistance. Just tag my name in the comment section below. Take care and have a great day ahead.

@jeni-tan 

As another option, you may utilize an importer tool

https://transactionpro.grsm.io/qbo

But if you migrate from a certain accounting system, you may consider purchase a 3rd party migration service.