I purchased a new iphone I want to clear all data and info from my old one How do I do it?

I purchased a new iphone I want to clear all data and info from my old one How do I do it?

Settings.
General.
Reset.
Erase all data and content.

Restore it to factory settings, you should see it on your manual.

Reset to factory settings and do not keep data

Use iTunes & the Restore option or on the iPhone itself in the Settings use the Erase All Content & Settings option.

I assume you've already transferred your data from the old one to the new one.

Factory reset.