Q: I want to remove an old iPad from my iTunes account. However, I could not find the Manage Devices icon in my iTunes account information page.
A: The Manage Devices page can normally be accessed from your main account settings page, found by choosing View My Account from the Store menu in iTunes. The option should appear in the iTunes in the Cloud section, immediately below your basic account information.
As the section heading implies, however, this is an iTunes in the Cloud feature, and may not appear if you have not used the iTunes in the Cloud features with your particular iTunes Store account from any of your devices. iTunes in the Cloud includes re-downloading previously purchased content from the iTunes Store, configuring iTunes or any of your iOS devices for automatic downloads of newly purchased content, or subscribing to iTunes Match. If you have not done any of these things, then it is possible that the iTunes in the Cloud section may be hidden entirely. Further, even if you see this section, only specific iOS devices that have been used with iTunes in the Cloud will be displayed here.
If you have not used your iOS device with iTunes in the Cloud, there is actually no need at all to “remove” your device from your iTunes account—simply wiping it and restoring it back to factory settings will suffice. In fact, this will generally be fine even if you have been using the iTunes in the Cloud features; the only reason you would need to remove your device from the Manage Devices section in your iTunes is to free up an additional “slot” for a future device, since you are limited to a maximum of 10 devices per iTunes Store account.