how to copy files but get alert that there is a duplicate

Currently, when I copy files from one folder into another folder using the copy command in finder, if there is already the same file in the destination folder instead of alerting me that I already have that file in the destination folder the system simply copies the file and appends "copy" to the filename (eg copying sound.jpg into a folder that already has sound.jpg becomes sound copy.jpg). Thus, I end up with a duplicate.

Similarly, when I download a file into my downloads folder that I have previously downloaded, it doesn't alert me that I am downloading a duplicate but downloads it.

Any tips on how to avoid creating duplicate files?

Thanks ever so much