I use
iPhone to PC transfer to help me copy all my iPhone music and videos onto my new laptop.
The whole process goes as follows:
Firstly install this program on your computer. When you connect your iPhone to the computer, this program would instantly display all music and videos on your iPhone. All you need is to select what you wish to transfer and click "Copy" button. Done. All your selected files will be copied to your selceted folder on the computer safely. Now you can easily add those files to the iTunes library.
More importantly, this won't overwrite any original files on your iPhone.
You can free download it to try and see if it works for you.