Invalid index name (Solr to ES)

I am trying to analyze Solr Data in Kibana. Hence, I am first transferring the data to Elastisearch through Solr River plugin for elasticsearch. I created the following index in elastisearch through this command in Linux:

curl -XPUT -d '
"type" : "solr",
"solr" : {
"url" : "",
"q" : ":"

And I am getting the following error

{"error":{"root_cause":[{"type":"invalid_index_name_exception","reason":"Invalid index name [river], must not start with ''","index":"_river"}],"type":"invali d_index_name_exception","reason":"Invalid index name [_river], must not start wi [root@auppol18 ~]#

I don't understand how it's an invalid index name?

Oh. And btw I am using the following tutorial:

Update: I have learned that the Solr River plugin has been deprecated and is not up to date.
Can anyone please tell me what alternatives I can use? I tried to find within the form but couldn't find anything.

I believe the _rivers are deprecated. It's better to do this work outside
of search anyway in a good ETL solution.

But for simple data transfers, we have this tool that we developed that we
use in our Elasticsearch consulting work