Evelyn just got a new iPhone and wants to transfer all her settings and data from her old iPhone 5. Leo says the first thing she'll want to do is backup the old one in iTunes. Make sure to select encryption, because it won't backup her passwords without it. Then she can plug in her iPhone 8 and iTunes will then ask if she wants to restore. She can just select that, and then it'll backup her passwords, download the latest apps, and any other data she wants. Here's a support page from Apple on how to do it.
But Evelyn should understand that music, audio books, and movies won't be backed up. She'll have to re-sync them to her iPhone. But the data, passwords, contacts, calendar, etc. will be synced.