How to charge my Apple Watch series 7 with no plug?

You either need to buy a USB-C plug or use a computer with a USB-C port. Here is one you can buy:

https://www.apple.com/shop/product/MHJA3AM/A/20w-usb-c-power-adapter?fnode=b67c15b8ec96f5cfdc9002dd33994c88027fa022f1f5caf5ef2d8377dcbc3553f91bb0365e1d34920ed2609c39d247916ab4688c4d5b0be9dd7b5d5efddc3549c55d1caf0afafb71360b1072ceffea368f3f83d8dae7740be50ca69962b14855393e92a49c7d3672998fe5bc4ce63a75

• If you had a previous Apple Watch, you can use that Charger
• If you have a computer with a USB C input, plug it into your computer
• If you have a USB C charging plug for another device you can use that
• If none of the above are available to you, you go buy yourself a 20w USB C charging plug. Apple sells one. Best Buy sells them. Amazon sells them. I like the Anker Nano 20w USB C plug and you can get one at Best Buy for about $16