How can you compare THE SAME of files in a folder when it's in separate, different hard drives?

If you plug the ESD into your Windows 10 computer, and you wish to refresh a folder (on the ESD) from a folder in the Windows 10 machine, so that only the files not on the ESD are transferred:

1. Open File Explorer in the source folder. Highlight all the files (e.g. by doing Ctrl-A on the keyboard. Right click any one of the highlighted files and choose "Copy".

2. Open the destination folder on the ESD and right click somewhere and choose "paste". If the file copier finds it would copy files already existing on the destination, it will pop up a dialog saying "The destination has X (a number) files with the same names." Underneath are 3 options, you can click ONE of them, or close the dialog to back out. "Skip these files" will only copy the files which are in the source but not in the destination.

Replace the files in the destination

Skip these files

Let me decide for each file

Update before I say thanks:

I lucked out big-time: I found some software that will compare a folder that might have a million files in it, when said folder is kept safe on multiple EHD's and uniformity is critically important.

The software has turned out to be a lifesaver and a time saver too because a missing file in a folder that has thousands of files

used to take 30 minutes or a lot longer

to identify

but now takes about one minute of time to identify the missing file(s).

Also, besides cutting down the time it takes to hunt down a file(s), after acquiring the software I learned that precision is no longer important, I can be sloppy and not worry about uniformity when creating new files and then storing them on separate EHD's -

like the night before I go to the bank and I need to be 1000% sure that both drives are uniform because I'm going to put the drives in a safe deposit box.

As soon as I downloaded the software this layperson saw some things and I was immediately hit with a good feeling by what I saw:

1) When you open the program you see 5 icons and one icon is labeled 'Folder Compare' (eureka !!! ... those two words spoke volumes)
2) Click on Folder Compare and then a window opens. Said window is split in half. At this point I was still trying to figure it out when up near the menu bar I saw a lot of icons but the one titled 'Diff' stood out like a sore thumb and I asked myself
3) Does 'Diff' mean it will compare the same folder that is stored on different drives? - boy, lets hope so. I soon learned that, yes, it is indeed the icon that compares folders and that is why
4) The window is split in half, because you drag and drop one folder, from each separate EHD, and into each half of the screen in order to compare the contents
5) You then click on 'Diff' and the program then HIGHLIGHTS the files that are missing
6) All of the above takes about one minute

After stumbling on the software I went to bed that night feeling as if I had finally eliminated a huge problem from my life. The next morning I was of course interested in the price, because I had downloaded a free 30 day trial - I learned that it costs $50, which I was kind of expecting.

Over priced? Oh heck yeah, but

since it can potentially save me a ton of time,

because I go to the bank on regular basis to swap drives,

and because you can't and never should put COMPLETE trust into online storage companies like Jungle Disk to protect your data,

the over priced $oftware is worth it to me.

Several years ago Jungle Disk lost ALL of my data when they made changes to their sites interface. The change to their sites interface,

coupled

with the loss of every single digital file I had, may, or may not, have been a coincidence. I will never surrender COMPLETE trust to any online storage service.

Sorry, but I can't, and will not, give out the name of the comparison software because you probably know why.

Tes yeux noirs,

I came back to this forum to thank you for taking the time to answer my important call for help that I lobbed towards the community and to wish you a Happy Labor Day 2015

Also, I found the software before I read your suggestion. I still have 27 days to use the software free of charge. I will try to use the procedure you noted to see if it works for me, thanks again.