[ColMac]

I'm looking at a book in the calibre edit book panels

I have a lot of em dashes which have apparently converted wrongly., and on the right hand panel file preview, it is displaying as a small empty square. On my Kindle, it displays as a rectangle with two "0"s at the top, and 97 below that.

It is easy enough to replace each one I find, but in the HTML view, the em dash is simply displaying as a space. Unfortunately not all of these em dashes were at the end of a line and followed by a ".

In many cases, they are in the middle of a sentence. I may be able to find them by searching for a double space, but presumably it must be a different character.

Any suggestions on what I should search for please.