One single physical HDD shows as 2 separate disks in Disk Management as Disk 1 and Disk 2. I need it to be one C drive disk, so C: Drive will be it's full 8TB and not just 256GB like the previous drive.

The picture shows that the boot and system drive is 256 GB one not 8 TB. How did you determine that the drive is corrupt and unusable?

Your 8TB Disk appears to be USB connected drive. This cannot be used as a boot disk.

It looks like you have a 256GB SSD and a 1TB (probably magnetic or possibly SSD) internal drive.The SSD was apparently the boot disk. It's odd that it's shown configured as RAID 0, which is ill advised.

You cannot merge partitions on separate disks.

Your options are to fix the boot order and SSD and use that as the system disk, install Windows on the 1TB internal drive and make that the boot disk. The best option, though with a cost, might be to upgrade the SSD to a 512GB or 1TB drive and install Windows there.

Since the original drive is corrupt and unusable, I really don't think that is what is showing .. I think it's the clone of that drive before it broke, that is on the 8TB drive. That is what I am booting from using the Sabrent enclosure, the 8TB drive. I am guessing my next task will be to take the laptop apart again, and pull the two 128GB drives? Will it be okay to leave those slots empty?

Seems M.2 drive is detected still.

Please show a screenshot of the Disk management. Run Device manager and show a list of disk drives.