The plural form if the noun guides is guides.
The plural possessive form is guides'.
Example: All of the guides' badges must be worn on their blazers.
The plural possessive form of "guide" is "guides'."
guides'
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.
Guides' is all the guides' stuff (plural possessive). For example: The guides' backpacks formed a circle. While guide's is one person's things (singular possessive). For example: The guide's dog ran away.
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 relatives. The plural possessive is relatives'.
The plural is stations. The plural possessive is stations'.
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 of rose is roses. The plural possessive is roses'.