I need three ______ of bread.

The correct answer is loaves. The word 'loaf' is a singular noun referring to a mass of bread baked in one piece. To form its plural, we follow the rule for nouns ending in -f or -fe: change the -f to -v and add -es. Therefore, 'loaves' is the correct plural form. 'Loaf' is singular and incorrect in this context as the sentence specifies 'three'. 'Loafs' is an incorrect pluralization and does not follow standard English grammar rules for this word.