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Unfortunately, this is currently not possible, as there is no “Search Data Store” endpoint in the Make Developer API reference.
You can also suggest for it to be made in the Idea Exchange. However, do search for a similar request (and also upvote), just in case it has already been suggested to avoid duplicates.
A workaround is to use the “List Data Store” items module/endpoint, before using a filter to filter the results by key.
Hope this helps! If you are still having trouble, please provide more details.
— @samliew
P.S.: investing some effort into the tutorials in the Make Academy will save you lots of time and frustration using Make!