How can I update my iOS

Here are two different ways to ensure the highest iOS that your device will support is on your device.

Update your iPhone, iPad, or iPod touch wirelessly. Click here --> Update your iPhone or iPad - Apple Support

Here are instructions about how to update your iPhone, iPad, or iPod touch with the Finder on a Mac computer --> Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

These are the instruuctions:--> Update your iPhone, iPad, or iPod touch but, before proceeding, check if your unidentified iPhone model supports more recent iOS versions, as per this compatibility list: