To find acronyms written in all caps in Microsoft Word, use the following search line (including the angle brackets) with wildcards activated:

<[A-Z]{2,}>

To find only plural acronyms, change it to this:

<[A-Z]{2,}s>

And to find only acronyms with an apostrophe followed by an s, change it to this:

<[A-Z]{2,}[’'´]s>