There are two accepted plural forms of the noun memorandum:
memoranda and memorandums.
The plural possessive forms are memoranda's and memorandums'.
Examples:
The memoranda's file is alpha by last name of sender.
The memorandums' file is alpha by last name of sender.
The plural of memorandum is memoranda.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural is lads. The plural possessive is lads'.
The plural is relatives. The plural possessive is relatives'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural of memorandum is memoranda.
The correct plural for memorandum is memoranda, but memorandums is also accepted.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
Memoranda is the plural form of memorandum.
The plural is lads. The plural possessive is lads'.
The plural is relatives. The plural possessive is relatives'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural form is stepsisters. The plural possessive is stepsisters'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is echoes. The plural possessive is echoes'.
The plural form is inches. The plural possessive is inches'.
Studies' is the plural possessive of study.