Step 1: Add the grams together.
600g+800g=1400 g
Step 2: Convert the total grams into kilograms and remaining grams.
Recall that 1kg=1000 g.
1400g=1000g+400g=1kg400 g
Step 3: Add this to the initial 2 kg.
2kg+1kg400g=3kg400 g
Therefore, 2kg600g+800g=3 kg 400 g.
3 done, 2 left today. You're making progress.