Copy pc files to mini

There is no application. You just copy the files from the external drive to the Mac, wherever you want them.

Though the confusion may be that Apple still insists on a "simplified" GUI for beginners. The issue being you won't see mounted drives on your desktop without turning that option on.

Click anywhere on the desktop so Finder is the name of the foreground app at the top left of the screen. Choose Finder > Settings. Under the General tab, turn on all four check boxes for the various types of connected drives a person could be using.

Your Mac's internal drive, and your external drive's icons should immediately appear on the desktop. Now copy files between drives the same way you would in Windows.

You should simply be able to connect the drive to the mini. It's likely formatted as NTFS, but that's not a problem. The Mac can copy from an NTFS drive, it just can't write to it.