grammatical number - How to Pluralize a Proper Noun That Already Has a "'s" In It

How does one pluralize a proper noun that already has an apostrophe in its singular form?

• for example, McDonalds'... How would I say there are three McDondald's in California?

Please note: I am not asking how to write a possessive form for a proper noun that already has a 's in it, I am asking how to pluralize a proper noun that already has a 's in it.

(The first instance has already been answered previously, and used McDonald's for an example as well)

Thank you!

Answer

So this is very similar to this question, but, as you note, not a true duplicate, because you're asking how to pluralize an already-possessive noun, rather than how to make it possessive.

However, many of the same tricks involved still apply. Namely, it's really best avoid the issue by rephrasing it in a manner which allows you to pluralize a different word instead, such as:

There are three McDonald's locations in California