Today's circuit is built from some excellent movements. Each of them will challenge your quadriceps, hamstrings, glutes, and stability muscles in ways they may not have been challenged in a long time. Even though it might be a little painful, this hard work is good for your body!
Do your best through all of the circuits. Select weight that will allow you to perform all 10 reps. If the last couple of reps on each exercise are difficult, then you've chosen the right pair of dumbbells.
Squats can be a difficult movement if you haven't done them in a while. Do your best to sit back like you're sitting in a chair. The movement should start with you moving your hips back, not bending your knees forward. If you need to, drop the dumbbells and practice the movement by sitting down to a bench and then standing back up.