Price level and purchasing power of currency(PPP)
Prices in themselves don't mean much when you want to predict purchasing power.
Imagine a loaf of bread costs 100 of country A's monetary units in country A, while it costs 2 of country B's monetary units in country B. This does not tell you anything about purchasing power because you do not know if you could buy a loaf of bread for 100 of country A's monetary units in country B or vice versa.
You also need to consider the currency A to currency B exchange rate, usually denoted by $E_{B/A}$. Then purchasing power/real exchange rate is calculated by
$$
\frac{P_A}{P_B} \cdot E_{B/A} ,
$$
where $P_A$ and $P_B$ are price levels in countries A and B respectively. If this is larger than 1, then using country A's currency one could buy more goods in country B than in country A, while if it is smaller than 1 then the reverse is true.