In theory, this isn't too bad. You'd create three subdirectories on the new drive, then do a deep copy of everything from your three source drives to the three subdirectories on the new one. That might be as simple as select-all-drag-drop.

At that point, you've now got the problem of convincing each old program that its data has moved to a new file path. I guess you're using Windows. You've got symbolic links, so if one of your old programs really, really knows where it wants to find its files, you can put a symbolic link there that points to the true location. (http://superuser.com/questions/1020821/how-to-create-a-symbolic-link-on-windows-10) The other trick is to assign a directory to a drive letter (http://lifehacker.com/267728/give-a-folder-its-very-own-drive-letter). That might be the easiest way to make the "new" environment pretend to be the old one.

I can't speak to the Seagate versus other drives. Just don't trust any one hard drive with anything. Backups, backups, backups!