To begin with, please head to the Gallery app and check the Pictures tab at the bottom of the screen, as any images captured or downloaded on to the device should be visible here. If you can't see anything, tap the 3 lines in the bottom right > Recycle bin, and check to see if the images have found their way here. If they have, press and hold on a photo, tap 'All' in the top left, then hit 'Restore'.
If the problem persists, close the Gallery app > Swipe up from your Home screen > Tap the Samsung folder > My Files. Are the photos visible in the 'Images' category towards the top of the screen? Similarly, if you select Internal storage > DCIM > Camera, can you see the missing photos here?
I also recommend heading to the Google folder in your apps drawer and tapping on 'Photos', as an archive of your images may be present in this location, depending on your Google account settings (Wi-Fi connection required).
