Hi Inquirer!
welcome to the Apple (user-to-user) Community!
Re: how do I locate the items that have been saved by the Save to Pocket extension?
Thank you kindly for the clear and precise info., you have included with your question
To: "See items you downloaded
- In the Safari app
on your Mac, click the Show Downloads button
near the top-right corner of the Safari window. - The button isn’t shown if the downloads list is empty.
- Find a downloaded item on your Mac: Click the magnifying glass
next to the filename in the downloads list. If you move a file or change the download location after downloading it, Safari can’t find the file."
Above is from: Download items from the web using Safari on Mac - Apple Support
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If more help is needed:
Seems Safari saves files to the location you have set in settings:
With Safari open,
Click Safari > Settings > Choose "General" from the top menu in the window that opens.
Look to see what is set for "File download location:"

You will likely find any files Safari downloads in that location.
if file still not found:
See what to do: If you can’t find a file on Mac - Apple Support for other ways. to find the file.
All the best :-)