TSQuery To Search Number and UoM in Text
FTS is very clever in some ways, but not very clever in other ways.  It is not clever (by default) in the way you want it to be.

You can set up a thesaurus to map words to synonyms, but I don't know if there is any way to get your hands on the " symbol in order to map it. And of course it is unlikely to make sense to convert every ", or for that matter every 'in', into 'inches'.