"Passers-by" is already plural.
The plural form of "passerby" is "passersby."
The singular form is passerby; the plural for is passersby.
The possessive form for the plural noun passersby is passersby's.Example: The passersby's attention is not drawn by our display.
The plural form for the compound noun passer-by is passers-by.
passersby
The noun 'passerby' is the singular form. The plural form is passersby.
passersby
Passerby
The plural form of "do" is "do" and the plural form of "don't" is "don't." These words do not change in the plural form when used in a sentence.
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "was" is "were."