Did it give you an error code? Might just be easier/safer just to swap out the old drive and install the new one first. Then initialize the new one in Disk Management and Win 10 should assign the next available drive letter, which should be D. Then copy your backup files onto the new drive. You have a backup of D, but you don't want to risk the old D drive until you safely have everything on the new HDD. But if you prefer, you can leave D connected, install and image the new HDD and assign it an unused  drive letter (Z: might not be a good choice). And after you remove the old drive, you can use Disk Management to assign drive letter D to the new drive.
My computer took 5 boot up attempts before it succeeded. I haven't turned it off since and everything working perfect. It did it's own self diagnostics, created a QR code of which I was able to order the failing drive under warranty with my phone, I was impressed. Now I got the drive, looking for the best way to do a seamless swap. I have backed up my system and did a second backup of D alone. I have a 4th SATA / power cable and was thinking of temporary initializing and formatting with "Disk Management" as a Z drive. The question is once it is all loaded can I unplug the failing D drive and then rename Z to D?  Also the system may not boot up again, wood it be better to remove the D drive and install new drive at the start? Interesting, chckdsk says there are ZERO errors on all my drive, it thinks all fine. Running Dell diagnostics again, it says D "failure" I can't find any videos on replacing one of three drive. I don't want to lose my data on C and F, I'm glad it's not the C drive, I'm hoping this is fairly simple. Please advise. 
XPS 8930, replacing failing "D" HDD with 3 drives under warranty