My camera isn't working

We need much more information. I will try to cover the basics to give us a starting point:

What do you mean, by "my camera won't show up"? Are you saying that the camera app has disappeared? Or if you open the app that the screen is just black? Or that you get an error of some kind?

Has it always been like this or is this a new development? If it is a new development, then there is a good chance of fixing it. If it has always been that way, it is likely a factory defect and needs fixing by Samsung; hopefully it is still in warranty.

Has there been any damage to the device, or any repairs performed? Damage such as dropping it could have disconnected a camera connector, while water damage could short out parts like a camera.

Have you tried other camera apps downloaded? Or other apps that can access the camera (such as snapchat) to see if it is a problem with the original app and not with the camera? If you can get another app to work, then the camera app you are using is faulty. See if you can update that app, or delete the data to roll back the latest update. It may not be possible to change the version you are on, but you could just use another camera app or wait until a new update comes to your original app to see if that fixes it.

If you get any kind of error, what is that error? Word for word, and include any error codes if provided.

If you can open a camera app but it is just black, try clicking on the zoom functions to switch to your wide angle camera, or the zoom camera, or the selfie camera. Your device has 4 cameras. Can you get one or more cameras to work? If so, it is likely a hardware error with just the camera(s) with a fault.

Looking forward to your response with more details so that we can try to help you out better, or perhaps one of these generalized ideas will help.