I don't even know if you can still buy Preps 6 because it is obsolete. The latest is Preps 7.5 and yes it can spit out a .jdf or a .pjtf. Take your pick.
System requirements for Preps 7.5 is:
Supported operating systems
Apple Macintosh OS X 10.9
Apple Macintosh OS X 10.10
Apple Macintosh OS X 10.11
Microsoft Windows 8.1 Pro
Microsoft Windows 10 Pro
Microsoft Windows Server 2008 R1/R2
You had also mentioned getting the CC subscription. System requirements for that are:
InDesign CC (2015) system requirements and language versions
Windows
Intel Pentium 4 or AMD Athlon 64 processor
Microsoft Windows 7 with Service Pack 1, Windows 8, Windows 8.1, or Windows 10
2 GB of RAM (8 GB recommended)
2.6 GB of available hard-disk space for installation; additional free space required during installation (cannot install on removable flash storage devices)
1024 x 768 display (1280 x 800 recommended) with 32-bit video card; supports HiDPI display
To use the new InDesign Touch workspace, you must have a touch screen enabled tablet/monitor running Windows 8 or above (such as Microsoft Surface Pro 3) with the screen resolution set to 2160 x 1440 or more
Adobe® Flash® Player 10 software required to export SWF files
Internet connection and registration are necessary for required software activation, validation of subscriptions, and access to online services.*
Mac OS
Multicore Intel processor
Mac OS X v10.9, v10.10 or v10.11
2 GB of RAM (8 GB recommended)
2.5 GB of available hard-disk space for installation; additional free space required during installation (cannot install on a volume that uses a case-sensitive file system or on removable flash storage devices)
1024 x 768 display (1280 x 800 recommended) with 32-bit video card; supports Retina display
Adobe® Flash® Player 10 software required to export SWF files.
Internet connection and registration are necessary for required software activation, validation of subscriptions, and access to online services. *
Windows 2012 R2