This Plurals - Changing Singular Nouns to Plural worksheet also includes:
In this plural nouns learning exercise, students change singular nouns to plural, and write the new word in the space provided. For some nouns, students need only to add -s/-es to the end of the word. For other nouns, students need to change the ending (i.e. loaf to loaves) or not alter the word at all (i.e. sheep).