Apple did their own thing! As such you need to use this custom case [product|IF107-154|External SSD Enclosure for Select Mid 2013 to Mid 2015 Macs] or [https://eshop.macsales.com/item/OWC/MAU3ENPRPCI/|OWC ENVOY PRO]
To learn more on Apples custom drives give this a read [https://beetstech.com/blog/apple-proprietary-ssd-ultimate-guide-to-specs-and-upgrades|The Ultimate Guide to Apple’s Proprietary SSDs]
I haven’t seen to many other options. There are a few PC cards which allow you to fit the drives into a Windows PC.