What's Best Way To Update A Picture Folder

When I save images they go to my download folder, after a while I then transfer and organize the picture files in my pictures folder.Sometimes though, some pictures have the same file name even though it's not the same picture. And other times there are duplicate files of the same picture. I copy and paste into the folder and usually select manually whether to move and replace, don't move and don't replace, or move and keep both files. But when it's 1000 files it can be tedious. I would like to only have one single copy of a picture.