Hello. Camera shots synced to Picasa or Google Photos are saved to your Google account. Check Settings - Accounts - Google - Sync Settings - Picasa, or Google Photos is checked and turn master Sync on.
You can go to your Google account on a pc and check them there.
https://photos.google.com/
https://picasa.google.com/
You can also drag your photo files to a pc via usb cable from the devices DCIM folder/s; or using the Samsung Kies (sync and/or back up) or the Samsung Smart Switch pc program to copy them that way.
They usually only sync in one direction, so once you're sure they are offline, deleting them from the S4 will not delete them from your Picasa (more recently called Photos) account.