QB Desktop provides the IIF feature for importing data but its capabilities are very limited.

You may have 2 options:

1, Purchase a third party conversion service.

2. Use the importer tool. It's a one-time $199 license and you can get $100 cash back for purchasing it through a partner. You will find templates for each type of transaction to import on their website.

https://get.transactionpro.com/qbd