Can't How to Replace quotation marks with smart quotation marks

The Preferences settings are for "As-you-type" correction, not for text clean up.

You need to do a Find and Replace Search:

Menu > Edit > Find > Find

[".] replace with [.”]

To replace the starting quote:

[ "]replace with[ “]

Use the samples here - only copying inside the square brackets.

You might try this on a copy of your document using the Edit menu : Find tool.

A left straight, or smart quote is usually preceded by a space, so in the Find facility, you want to enter a space followed by the straight double quote. The replacement will be a space followed by a smart double-quote, or the keyboard sequence option + { on the U.S. English keyboard.

The right straight, or smart double-quote usually ends with the quote followed by a space, so that is your Find sequence. You enter the replacement string as a smart quote as the keyboard sequence option + shift + { that is followed by a space.

This will still leave any straight quotes that begin a sentence. You will have to fix these manually, as the Find tool will attempt to replace all previously changed straight quotes with the left smart double-quote.

"on my keyboard" does not tell us what keyboard you are using.

I am using Australian/US keyboard.

You may have to look at your keyboard to find where the specific characters lie, but I gave you the Search & Replace above, you can just copy from that.

Download the free WordService by Devon Technologies from the Mac App Store. Among the many, many services it includes is changing from straight to smart quotes (& vice versa).

I did mention that the option+{ and shift+option+{ work on a U.S. English (Apple) keyboard, because that is what I frequently use to force opening and closing smart double-quotes.