Replace whole paragraph on multiple pages

A SQL query should work for you. As seen here:

Search and Replace WordPress Post Content

To search and replace post content, use the following code. Replace
OriginalText with the current text and replace NewText with your new
text.

UPDATE wp_posts SET 'post_content' = REPLACE ('post_content',
'OriginalText',
'NewText'
);

I would try this “SearchReplace” plugin myself.