When we copy and put two folders with the same name together, the files in the folders are being replaced rather than merged. Is there a way to change that behaviour?

Merged as in, For example:
There's a new Folder A and an old Folder A.
The new Folder A has new files that are not existing in old Folder A.

If I copied the new Folder A to replace the old Folder A, the files inside old Folder A will be removed entirely and replaced with all the files in new Folder A.
But if I do that in Windows, new files in new Folder A will sort of "append" to the existing files in old Folder A.


I just did that copy and paste folders in my mac and my files are now missing...