Plural acronyms and abbreviations
There are different ways to form plural acronyms and it highly depends on the individual acronym or abbreviation. Please look up the plural acronym or abbreviation if available. Otherwise, you may add the apostrophe or omit it to avoid misreading or confusion.
"PhD" → "PhDs" | "M.D." → "M.D.'s" | "FPS" → "FPSes" |
More info: https://www.thepunctuationguide.com/apostrophe.html#plurals