Macrium Reflect – how to reverse its partitioning?

I have two identical USB drives: WD-Elements-(A) & WD-Elements-(B) each having a nominal capacity of 2 TB. Some time ago, whilst experimenting with the free Macrium Reflect, I created an image of my PC onto WD-Elements-(B) leaving me with just 359 GB of accessible data space on that drive.
How do I now reverse that partitioning so that I can use the whole of the disk space for data? Only the 359GB partition is accessed when I attempt to format the volume.
The partitions on the two drives are shown as:

MikeinGrange said:

..., I created an image of my PC onto WD-Elements-(B) leaving me with just 359 GB of accessible data space on that drive...

If (B) is the upper of the 2 disks displayed, I suspect you made a clone rather than an image. If you mean you just want to clear out that drive to use it all (creating a single volume on it) then yeah, MiniTool that fireberd referred you too will make short work of that.

Is it something other than what I described that you want to do? Did I misunderstand and you are booting from and using the upper disk as your system disk? I see a 359 GB used on that disk but no 359 GB remaining of any status anywhere.

Great that you got it sorted, Mike!