afaik a duplicate will not retain the cloth sim because the sim cache data is keyed to a particular object in a particular file, and the cache data isn’t duped with the new mesh.
In order to retain the original cloth sim and “extract” a particular frame, you’ll need to duplicate both the cloth sim data cache (labeled “blendcache_<filename>”) and the .blend file that wrote the cache data. So first copy the cache data folder and paste it into the same directory, then rename it “blendcache_<new-filename>”. Then save your .blend file as “<new-filename>.blend”. Of course you can put whatever filename you want in between the "< >"s, and the brackets aren’t necessary. Then in one or the other of the identical-except-for-filename .blend files, use either Apply or Apply as Shape at whatever frame you want to extract. I usually always use Apply as Shape because it makes editing the converted cloth mesh handier, you retain both the original mesh shape and the cloth frame, and can make edits on a new shape key made with W-KEY>Blend from Shape. Once the edits are final the other shape keys can be deleted if desirable to do so.