Velocity does not have unit give reason

Hi how are i have some questions about english subject can you answer for me ?

In the first line of each stanza, the author follows the pattern of a noun followed by a pair of adjectives. what is the purpose of this pattern?

At four hundred miles they stopped to eat, at a thousand miles they pitched their camp. they had traveled for just three days and nights, a six weeks' journey for ordinary men. this excerpt is repeated several times. how does this repetition affect the epic?