1000 ml = 1 L so 2100 ml = 2100/1000 L = 2.1 L. Simple!
The "mill" in millilitres means thousand, so ... 1 litre (L) = 1000 millilitres (mL) So 2.1 L = 2100 mL
1.29 L
9,000 mL = 9 L
1.25 L = 1250 mL
4 mL = 0.004 L
350 L = 350,000 mL
5.03 L = 5,030 ml
398 mL = 0.398 L
26.78 mL = 0.02678 L
102 L = 102,000 mL
0.0817 L = 81.7 mL
0.01 L = 10 mL