Motivation

You want to back up and restore your photos on a MacBook.

Solution:

To back up your images:

1. Quit Photos app.
2. Go to /Users/yourname/Pictures.
3. Copy Photos Library.photoslibrary to your backup location.

To restore your images:

1. Quit Photos app.
2. Copy Photos Library.photoslibrary from your backup location to your MacBook.
3. Hold down the Option key and double-click the Photos app.
4. In the Choose Library dialog, select your Photos Library.photoslibrary.
5. Click Choose Library button.

To back up your music:

1. Quit Music app.
2. Go to /Users/yourname/Music.
3. Copy Music Library.musiclibrary and Media folder to your backup location.

To restore your music:

1. Quit Music app.
2. Copy Music Library.musiclibrary and Media folder from your backup location to your MacBook.
3. Hold down the Option key and double-click the Music app.
4. Click Choose Library… button.
5. Select your Music Library.musiclibrary.
6. Click Choose button.
7. You may also go to Music > Settings… > Files  and change Music Media folder location.