It depends on the scale.
Some scales (called balance scales) balance your weight against the weight of a known mass. Your weight is a force, calculated as mass x acceleration. The weight of the known mass is calculated the same way. Generally, there's some kind of adjustable leverage for the known mass. The scale is calculated by measured weight of known mass in the lab x multiplier used for leverage = weight of person on scale. So if the mass weighs 3 lbs, and there's a 50x multiplier at a specific notch on the scale, then the mass is putting 150 lbs of force on the lever in one direction. If the lever is balanced at that setting, that means you have to weight 150 lbs.
But there's an "error" here. The weight of the known mass depends on the acceleration in your reference frame. If you're on the moon, the mass weighs only ½ lb, so it's only putting 25 lbs of force on the scale, so you only weigh 25 lbs. But the painting on the scale doesn't change, so it's wrong. Technically speaking then, the scale measures mass, not weight, and the numbers should reflect mass. So instead of 150 lbs, it should read 68 kg, or 10 stones, etc. Of course, the scale isn't intended to be used outside of Earth, so the "error" is just a simplification. Because you're actually on Earth, and the scale knows you mass 10 stones, you do, in fact, weight 150 lbs.
Now, spring scales operate differently. In this case, your mass is accelerated by gravity to put a force against a spring of some type. The spring's compression/expansion rate is independent of acceleration, so the length of displacement is directly proportional to the force you're putting on it. If the spring has a rate of 100 lbs per inch, and you're displacing it 1.5 inches, that means you're putting 150 lbs of force on it.
If you move this to the Moon, gravity is only accelerating you at 1/6 g, so you put 25 lbs of force on the spring, and it will only displace 1/4 inch. This 1/4 inch displacement will be correctly measured as 25 lbs.
Technically, pounds are a measurement of force, and kilograms are a measurement of mass. In the real world, however, we typically use them a bit interchangeably. If I say "this has 200 lbs mass", I mean it's mass is enough that it would weigh 200 lbs on Earth. If I say "this weighs 68 kg", I mean it is putting the same force on the scale as a 68 kg object would on Earth.
So a spring scale, measuring weight, might use kilograms as the unit. Technically, that's wrong, because the scale measures weight, not mass. But as long as you're on Earth, the mass is correct. Just like the mass scale can correctly state your weight on Earth.