how can I retrieve a device I deleted from my account?

There isn't a list of devices you have deleted from your Apple ID. You can only see where you are signed in.

To add a device, from the article below.

https://support.apple.com/en-us/HT205064To add a device to the list, you need to sign in with your Apple ID. After you sign in on a device with your Apple ID, that device appears in the list. Here's where you need to sign in:

• For iOS 9 and later, sign in to iCloud, iMessage, FaceTime, iTunes & App Stores, or Game Center on the device. You can also see your paired Apple Watch.
• For iOS 8, sign in to iCloud or iTunes & App Store on the device. You can also see your paired Apple Watch.
• For OS X Yosemite and later or Windows 10 and later, sign in to iCloud on the device. 
• For Apple TV HD and later, sign in to the iTunes and App Store on the device.
• For Apple TV (3rd generation) and earlier, sign in to the iTunes Store on the device.
• If any of your devices are using earlier versions of iOS, OS X, or tvOS, you won’t see them in your device list.

Check your Apple ID device list to see where you're signed in - Apple Support