How to charge Apple Watch Series 7 (2021) or 8 without or with the charger and check the battery. No USB-C adapter is included in the box, but the old USB-A cables still work (just not as fast).
Apple 20W Power Adapter Amazon US (paid link): https://amzn.to/2HwzPk5
Apple Watch USB-C Cable Amazon US- included in the box with Series 7 (paid link): https://amzn.to/30SewU0