The term 'Pick a number from __...' is completed by the three-letter word 'ONE'. This phrase is often used to indicate that someone should choose a single number from a range of numbers. It is commonly used in games and puzzles, such as crosswords, where the player must select a specific number from a given set of numbers. It can also be used in everyday conversations, when someone wants to ask another person to pick a number from a range of numbers.