If you have an older Garmin watch (like a Fenix 6 or Forerunner 945), you can add power data by pairing it with a specific accessory:
Garmin HRM-Pro / HRM-Pro Plus (Chest Strap)
Garmin Running Dynamics Pod (Waistband Clip)
Native Wrist-Based Power (Built-in)
Most modern performance watches now calculate power directly from the wrist. While a pod is more accurate for wind and form, these are excellent "all-in-one" solutions.