I t  does not fit into iPhone seven either and I don't see anything about additional hardware besides the Square. I don't know what kind of adapter,if there is one, to use

The iPhone 7 and iPhone 7plus both removed the headphone jack.  But luckily the iPhones came with an adapter in the box to support legacy hardware.  So you have everything you need, your old square, and the iPhone lightning to headphone adapter, and the iPhone 7 with lightning port only.

I have an iPhone 7 and from I read here, it has an adapter for the Square?  I need to find the equipment that came with the phone and try to make it work!  If I can't find the orginal purchase equipment, can it be purchased from my phone carrier?  T-Mobile?

https://www.apple.com/shop/product/MMX62AM/A/lightning-to-35-mm-headphone-jack-adapter?fnode=97

@sherideloach17 Any store may have one like a Best Buy, Walmart, maybe a phone store. It is a lightning to 3.5mm headphone adapter. Usually around $9, but included with your new iPhone. 

Hey @Liza1! To add to VanKalkerFarms' suggestion, we also have our own adapter available for the Magstripe and Chip readers. Or you have the option to upgrade to the Contactless reader which connects via Bluetooth and will accept Apple/Android Pay.

I have not seen that before.  very interesting.

@VanKalkerFarms - It was released last month! 🙂