A numeral can usually be made clearly plural with an S (2s, 3s), although traditionally using an apostrophe for letters and numerals was one of the few exceptions to the rule that apostrophes are not used for plurals.
Examples:
There are three 2s and two As in the product number.
(three 2's is no more clear, but A's looks less like "As")
He was born in the 1960s. He died in the 80s.
(just as clear as 1960's, but using '80s shows it was a decade, not an age)
The abbreviation for number is No. (has a period at the end). Numbers plural is Nos. (again a period at the end).
The plural of "half" is halves.
The plural form of radius is radii.
des ciseaux (masc., plural)
xes. The plural, sexes, is a palindrome.
The plural of ostrich is ostriches.
The plural possessive is others'. You simply add an apostrophe to a plural ending in 's' to make it possessive.
The abbreviation for number is No. (has a period at the end). Numbers plural is Nos. (again a period at the end).
There is more than one month, so the plural form is used. The correct term would be '5 months'.
The plural way to spell studio is studios.
The plural is resources.
The plural is cantaloupes.
The plural is roses.
The plural is "emeralds."
The plural is cherries.
The plural is hooves.
According to several dictionary sources and a number of scholarly types, "addenda" is the plural of "addendum", and not "addendums" as most spell checkers will accurately mark as wrong.