Quicken for PC imports QFX (Web Connect) and QIF files, Quicken for Mac imports QFX and "CSV Mint" files. For QFX files your Quicken version must be not older than 3 years. For example, for current 2018, the oldest Quicken importing QFX files is Quicken 2015 until April 30 and then Quicken 2016 is the latest one allowed to import QFX files.
For Quicken 2017 for PC, you must have a Deluxe version or better to import QIF files, the Starter version imports into a cache account (but you can move transactions from proxy cache account to another account after import).
Quicken 2018 for PC (all editions including the Starter edition) is the first version in many years that "officially" imports QIF files without any scary warning messages.
If your Quicken for PC is older than three years, your only option is QIF files.
If you have Quicken 2016 Release R7 for or later for PC and importing transactions for non-USD account, your only option is QIF files. If you have Quicken 2015 or Quicken 2016, to import QIF files you must use a proxy cache account to import
transactions there and then move transactions under another account.
If you have Quicken 2007 for Mac, your only option is QIF files.
If need to import transactions as QXF (not QFX) format, please leave this idea and check available formats below. QXF format is encrypted format to move data (whole data file) from one Quicken to another. Quicken changes QXF format every year and it is different for PC and Mac versions, and with other formats available QXF format is useless overall for the current version of Quicken.
Download CSV2QFX and install it
Start CSV2QFX and point to the CSV file (make sure it is not opened in Excel)
Enter the account ID as select the account type
Click the Convert button to create the QFX file
If the account in Quicken is connected to direct bank download, disable online services before importing a QFX file
Import the QFX file into Quicken as Web Connect file
Download CSV2QIF and install it
Start CSV2QIF and point to the CSV file (make sure it is not opened in Excel)
Enter the account NAME exactly as you have in Quicken
Make sure to select the QIF target matching your Quicken version
Click the Convert button to create the QIF file
Import a QIF into Quicken (import Quicken messages about supported account types)
For Quicken 2015-2016, select proxy cache account, for Quicken 2017, 2014 or earlier select All account
Download CSV2CSV and install it
Start CSV2CSV and point to the CSV file (make sure it is not opened in Excel)
Click the Convert button to create a CSV Mint file
Import the CSV Mint file into Quicken
Notice transactions will be imported into a new account, select all transactions and drag then to another account