itunes not letting me restore backups

Hey e_m_r15,

Welcome to Apple Support Communities.

It sounds like there’s an issue restoring your iPhone 6 Plus from a backup of your iPhone 5c. If you haven’t already, take a look at the article linked below which provides a lot of great information about transferring content to a new device.

Transfer content from an iPhone, iPad, or iPod touch to a new device - Apple Support

Get ready

Install the latest version of iTunes on your computer and the latest version of iOS on your original device.

You can't install a backup of a newer version of iOS onto devices that are using earlier versions of iOS. If your backup came from a device that has a newer version of iOS installed, update your new device before you transfer your data. For help, see Unable to restore from a backup of a newer iOS device.

Take care,

-Jason