So now it's back to Macrium; this is like a ping-pong game.
Anyway, here are some instructions for cloning the contents of the "second" 2 TB HDD to the second partition on the 4 TB destination drive...
1. Open the Macrium screen
2. Click on the 2 TB source drive that contains the data contents you want cloned to the appropriate partition on the 4 TB destination drive so that the schematic of the source disk will be outlined; then click "Clone this disk" just below the schematic.
3. A window will open showing the "Source" drive as the disk selected to clone.
4. Click "Select a disk to clone to..."
5. A smaller window will open showing the potential destination drives, i.e., your boot drive on which you installed the Macrium program...