Nothing on a stockroom shelf was born a solution. Somebody weighed a solid, and a chain of small conversions carried it to the label: grams become moles through $n = \dfrac{m}{M}$, moles become a concentration through $C = \dfrac{n}{V}$, and if the job calls for something weaker, $C_1 V_1 = C_2 V_2$ finishes it. Three formulas you already own, holding hands.

The discipline of a chain is bookkeeping: write each link's answer down, with its unit, before reaching for the next. Each formula's output drops straight into the next one's socket — and every conversion (millilitres to litres, always) happens at the socket's edge, never inside the formula. A chain is only as honest as its most careless link.