The cubic metre (or cubic meter; US spelling) is a unit of volume and is derived from an SI unit with the symbol m³.
1 cubic metre is exactly 1000 litres. It is also ≈ 6.29 barrels, ≈ 220 imperial gallons and ≈ 35.3 cubic feet.
1 cubic metre of water in normal conditions (≈4 °C) weighs exactly 1000 kg (or 1 tonne).)
The cubic metre is the unit used to measure water usage and often water bills are broken down into how many m³ has passed through the property / business.
The peck is a unit of volume in the US customary unit system. It uses the symbol pk.
1 US peck is equal to 1/4 of a US bushel. This is also equal to 2 US dry gallons, 8 US dry quarts or 16 US dry pints. In SI / metric, this equates to 8.809768 L.
Although the imperial peck is almost obsolete, it survives in some places in the USA - where some products (namely apples) are still sold by the peck.
It appears in the old English nursery rhyme; 'Peter Piper' where he 'picked a peck of pickled peppers'.