Use the Transactions app to convert your transaction files to required by your accounting software file format.
When the QIF file is created, switch to Quicken and import created QIF file. Make sure to backup your data. To import a QIF file, select 'File' - 'File Import' - 'QIF File', select created QIF file.
For Quicken 2017 or earlier, it is important to select ''All Account''. For Quicken 2018 or later, you have to select the actual account.
Then click the 'Import' button.
Then click the 'Done' button.
Now your data is imported. You can review transactions and use Renaming Rules if you like. Then click 'Accept All transactions'.
They accepted and listed in Quicken.