How to transfer photos back to camera?

A while ago i accidently deleted some pictures from my memory card. I have them saved on the computer. I want those photos back onto my camera memory card so that i can print them off. How do paste them back? I've already copied and pasted them onto one of the folders of my nikon camera. When i put the memory card in the computer, i can see all of the images but when i put the card in my camera, i can't see them. What am i doing wrong?

Added (1). Ok i got it to work… But none of you were answering my question

You can do that using your file manager, but the image files will no be seen by the camera. Memory cards are for temporary storage only and are not meant to be used as a library of images that are accessed by the cameras so you can display your fine work later

The steps one should take are these:

At the end of each shooting day, copy all the image files to your computer to a new file folder named for the subject and date. Sample NewCar0212.

Once all the images are safely on the hard drive, you need to format the card using the format feature on the camera. Always carry a spare memory card so that you are not tempted to delete image files from the inserted memory card to make room for more files. This habit almost guarantees that the memory card will eventually become corrupt and you losing your files

You haven't done anything wrong. Cameras aren't viewing devices. It will only preview unmodified pictures it took. Other more smart models will not even honor images taken out then returned especially if the folder, the date and the order of filing is different. The pictures are still there. If you want to show off pictures, you can use your cellphone or other multimedia players.

I know you've got it to work - good on you
But i'm pretty sure that if you couldn't view them on the camera, it doesn't really matter when you take it to a printing place because if you know they are on the memory card then the printer will pick them up