The plural form of the noun datum is data.
The plural possessive form is data's.
example: You must substantiate your data's reliability.
The plural of datum is data. The plural possessive is data's.E.g. The data's theft put some customer accounts at risk.
The possessive of all English plural nouns NOT ending in s is formed by adding 's: men's
The plural form of the noun month is months.The plural possessive form is months'.Example: Next month's schedule has been posted online.
The plural form of the noun address is addresses.The plural possessive form is addresses'.example: All of the addresses' accuracy has been verified.
Yes, "datum" is the singular form of "data." However, in common usage, "data" is often used as both singular and plural.