what value goes here?
It looks like the Hive HTTP data source in Redash is meant to be compatible with a Hive server that operates in HTTP Mode. From the linked documentation:
Currently, you can run HiveServer2 in either TCP mode or the HTTP mode, but not in both.
And it provides a list of options. Beyond that you might need some trial and error to get the right URL. I don’t use Hive so I don’t have any more specific guidance.