How do you compare THE SAME files in a folder when they're in different drives? (hard drive, transfer)

[Grass Cutter]

I have a C-Drive (Windows 10) and several EHD's (external hard drives).

The EHD's mirror what is on the C-Drive, I use the EHD's to back up the exact data, the exact number of files, that are found on the C-Drive.

Problem: Sometimes my C-Drive might have a folder that has way more files in it than the EHD does. For example, the My Pictures folder located on the C-Drive

might have 1,100 files in it

and the same folder (My Pictures) located on the external hard drive might have less,

950 files in it, for example.

Is there a procedure (or a software program) that will

quickly find, highlight, and point out

the 100 outstanding files so a person can transfer them over to the EHD?

My EHD's are remotely stored in a safe deposit bank at a chosen bank. I swap them out, or rotate them, about once a week.

If you're a code king or code queen then please dumb your answer down, way down, because I'm a simple person who mows lawns for a living, thank you

Jennifer

My OS: Windows 10

[Skunk Workz]

There are a number of programs that can do this:

Beyond Compare is pretty much the top of the line, but it's not free.

Scooter Software: Home of Beyond Compare

WinMerge is free, but may not be quite as full featured, or as user friendly.

WinMerge

[DPolo]

Google free software that suits your purposes. You might find something awesome for $20 license fee. For me it's easier to write a program like this then to find one, and then you have to install it. And you know what ? It will ask you to reboot. It is seriously easier to write one then to look for a good free version for me.

[LeaderOCola]

if you are comfortable in the command shell, there is a simple solution described here
How to compare two folders in Win 7 prof 64bit - Microsoft Community