How to import and restore music files to and from iTunes?

How to import music to iTunes?
Sometimes, you may have some music files and you want to listen to them on your computer. You need to add them to your iTunes. Actually, you can do that easily.
First, launch iTunes on your computer.
Second, click File to import the audio files into iTunes. You will see the progress bar when iTunes process these files. If you export music files with artists and name, it will automatically organize according to the the information like name, album. But you can change them by manual.

But in this way, you do not really add the music files to iTunes, they just list in iTunes and you only put the shortcut of these files into iTunes. If you change the location of these music files on your computer, the iTunes cannot find them and you can never play them in iTunes. Therefore ,to let the iTunes keep your music files, you should copy files into iTunes. Next time you still can play these music files even if you remove them or delete them.
In iTunes, click Edit>Preferences…>Advanced, check the option “Copy files to iTunes media Folder when adding to library”. You can check them in iTunes folder on your system drive.
First, you can recover your lost music files on iPhone from previous iTunes libraries folder
Exit iTunes app on your computer.
Find your iTunes music libraries in your Windows in the path: \Users\Username\Music\Previous iTunes libraries. You can find files with the file extension “.itl” and a date.
Rename these files with .itl extension and iTunes library.xml.
If every thing goes well, you will find your lost music files in iTunes.
Second, you can recover your music files with data recovery software
Launch H Data iPhone recovery software on your computer and click “View and Restore from iTunes backups”.
Select a backup and click SCAN button. You can configure by the device name, time and serial number. Or you can select the iTunes backup on your computer by manual.
After scan, you can preview all the contents that you have backed up.
Check the files you need and export them to your computer to save them selectively.
In addition, you can restore your music files from Cloud
If you lost your music files that purchased in iTunes, generally, you can restore in iTunes. Sign in with your Apple ID and password.
Click More option and select “Purchased” tab to choose “Music”. Select music you want to restore and click the cloud icon to download them.