The word snowmen is plural (the plural of snowman).
The plural possessive is snowmen's.
Example: The snowmen's remains could be seen on the neighborhood lawns.
The singular form of the plural noun snowmen is snowman.
The singular possessive form is snowman's.
Example: The snowman's hat blew away in a strong wind.
As I rounded the corner in a temperate zone, there I spotted many snow upon the land.
The possessive form for the noun snow is snow's.
Example: The snow's brightness made the scene look clean and fresh.
The plural of snowman is snowmen.
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.
The correct form is "its" for the possessive form in the plural. "Its" is used for both the singular and plural possessive forms, without an apostrophe.
The plural is briefs. The plural possessive is briefs'.
The plural is lads. The plural possessive is lads'.
The plural is trollies. The plural possessive is trollies'.
The plural is stations. The plural possessive is stations'.
The plural is relatives. The plural possessive is relatives'.
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive form is heart's; the plural possessive form is hearts'.
The plural form is homes; the plural possessive is homes'.
The plural of rose is roses. The plural possessive is roses'.