Begin by strongly driving up while keeping your back flat. The first part of the pull is slower. Then as the dumbbells pass the knees, the knees and hips will scoop under the bar. Continue to drive up strongly so that the ankles, knees and hips are all at full extension while the shoulders complete the upward momentum by shrugging.
As the dumbbells continue upward, drop your hips and pull yourself into a front squat position with the dumbbells resting on the shoulders. Finish the movement by driving up just like the front squat.