Logging in to iPhone 6 and iPhone 5S

If these phones are passcode-locked and you have forgotten the passcodes, see

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

Resetting an iPhone will wipe all data stored on it. If there is data that does not exist elsewhere, in backups, iCloud, etc., it will be lost. To reset an iPhone that has Find My turned on, you will need to enter appropriate Apple Account credentials to satisfy Activation Lock.

If these are second-hand iPhones, and are Activation Locked to someone else, see

The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community

Activation Lock is a theft deterrent feature with no bypass or workaround.

Without the owner's authorisation (Apple ID & password), no thief or anyone including you can re-use the device.

You can recycle the device responsibly.