As you can see, there is no picture included in your post.
However, from what you have said, it sounds as though you see a message telling you that all the content of your iPod will be deleted and replaced by the content of your current iTunes Library. If so, that is because you are trying to synchronise your iPod with a different iTunes Library to the one used in the past. This may be because:
- you're using a different computer
- it's the same computer, but it has been repaired, so iTunes regards the iPod as a new connection
The result is that it will delete all the existing content and put onto the iPod only what is in your Library. In either case, you need to ensure that your music is stored on your computer and playable, by iTunes. You cannot simply copy from the iPod back to your computer.
If it's a new computer, you need to copy the music folder from your old computer to the new one and make sure its playable in iTunes before going any further. If its the same computer, you need to re-build your library from a previously made backup. If you don't have a backup, then you will need to rebuild from the beginning. There are third-party programmes that can help with that chore. See this tip from fellow user turingtest2: Recover your iTunes library from your iPo… - Apple Community for further information.
Once you have all your music in the new library, you can sync the iPod with it. What will happen is that iTunes will remove (delete) the content of the iPod and put on the content of the current library. So providing your library is the same as the content of your iPod, you will not lose anything. Make sure that you understand this point; if you synchronise your iPod with a different iTunes and ignore that message, you will lose the content of the iPod - unless the new library has the same content.