My charging cord for my Apple Watch doesn’t fit the adapter

Apple Watches currently ship with a USB-C cord. If you don't have any USB-C power adapters or devices you can purchase one from Apple or from 3rd parties. One example is Buy 20W USB-C Power Adapter - Apple

Another good option, which you can purchase from just about any BestBuy store is the Anker Nano 20w USB C charging plug --> https://www.bestbuy.com/site/anker-powerport-pd-nano-20w-high-speed-usb-c-fast-wall-charger-for-iphone-or-samsung-white/6447411.p?skuId=6447411