Welcome to the forum. Light is measured in PPFD (photosynthetic photon flux density.) You can measure PPFD with a phone app called Photone.
In general, the minimum is:
Seedling stage: 300 PPFD
Veg stage: 600 PPFD
Flowering stage: 800 PPFD
PPFDs above 1,200 are about the limit. You can give a plant more, but there are diminishing returns above 1,200 without the use of CO2.
Cannabis is a very light hungry plant and you should give it all of the light you can via adjustment of the light’s wattage or by varying the light’s distance from the canopy. If you can feel heat from the light on the back of your hand when you hold your hand at the plant’s canopy, then the light is too close. Anything else is fair game.
DLI (daily light integral) is also a great method for determining how to manage your lighting.