If the amount of files is huge, you could just remove the main disk (OS) property from old HDD with Disk Management/an bootup HDD utility and so on plug it into your new system and let it be recognize with 1) either Windows of the new system (use Disk Management again and let it detect) and use This Computer/File manager to copy, OR 2) Just plug it in next to the new HDD, in the new system and use an bootup File Manager utility (guess: Hiren's Boot, google it) to copy all files from old disk to a new folder on your new HDD, they mostly work with an Manager gui and great utilities for this are available.
Simpler said, just connect it with SATA and maybe even for the convenience choose your main disk for Bootup (priority) menu instead of all advanced ways as above this might also just work fine
I'm putting this here incase you have many files and it's better for convenience or something to mass-move it. If not, just do it with storage media as Trekzone said