How To Change Straight Quotes To Curly Quotes In an Existing Pages Text?

A have a large text that’s already written in the Pages app: it’s about 50,000 words. The writer has used straight quotes throughout; I want to change these to curly quotes throughout. But how? Is there a find-and-paste solution?
I’m an editor and this problem comes up all the time, and all I can do is go through the manuscript, manually changing straights to curlies. I’ve had enough of this!
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Dr Steve