Getting your 1SE to a new device is super easy! First step is to make sure you have an iCloud backup with 1SE on it. The best bet is to do one last backup on your old device. Sadly, there's not a way to view what's inside an iCloud backup once it's done. So best to be safe and do one last backup!
Once you have your iCloud backup, simply select to restore from iCloud and log into your iCloud account. This will show all your backups on iCloud. Select the most recent one and agree to the terms & conditions. Then hang out and grab a coffee. It'll take some time to restore via wifi.
Want to use iTunes to restore instead? Here's how you restore using iTunes.
Want to learn how to backup your 1SE using iCloud or iTunes? Here's how to backup your 1SE.
TIP: It's very important that the backup you restore from includes 1SE. Without it, your 1SE won't be uploaded to the new phone.
VERY IMPORTANT: Please keep in mind logging into iCloud isn't the same as an iCloud backup. 1SE is NOT saved in your iCloud account. Only basic data like notes, mail, and contacts are. You'll need to do a backup via iCloud or iTunes.