Help! How do I retrieve and add playlist to iPod nano from new iMac?

Use the Finder to sync your iPhone, iPad, or iPod with your computer - Apple Support

An Apple Music subscription and associated playlists isn’t compatible with an iPod nano, if that’s what you’re trying.

You can sync all or a selection of your music on your Mac to your iPhone, iPad or iPod touch.

Important: If you subscribe to Apple Music, your music is transferred automatically to all your devices and no syncing is required. You can’t use the syncing method described here unless you turn off the Sync Library option in Apple Music preferences.

Sync music to your device

1. Connect your device to your Mac.
2. You can connect your device using a USB or USB-C cable or using a Wi-Fi connection.
3. In the Finder  on your Mac, select the device in the Finder sidebar.
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5. If you connect your device to your Mac using a USB cable and can’t see the device in the Finder sidebar.

1. Click Music in the button bar.
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3. Select the “Sync music onto [device name]” tickbox to turn on syncing of your music.
4. With the tickbox selected, syncing is set to transfer all your music to your device. 
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6. To sync a selection of music, click “Selected playlist, artists, albums and genres”.
7. Select the tickbox for each item you want to sync in the music list. Deselect the tickbox for any item you don’t want to sync.
8. Click Artists, Albums, Genres or Playlists to see your content organised by that category. 
9. Select syncing options: 

• • Select the “Include videos” tickbox to include videos when syncing.
  • Select the “Include voice memos” tickbox to include voice memos when syncing
  • Select the “Automatically fill free space with songs” tickbox to have your Mac fill the free space on your device with songs when syncing. Use this option if you have a large music library on your Mac but don’t have room to sync all your music to your device. This option syncs as many songs as possible.

1. When you’re ready to sync, click Apply.

You can choose to sync your Mac and your device automatically whenever you connect them.

Before disconnecting your device from your Mac, click the Eject button  in the Finder sidebar.