@dadoonet I tried this approach and seems like index not found error i was getting.
I followed this page added remote server info to ES.yml file on source side where i have lower ES version(v5.6) and setup ES on destination side with(v8.7).
After that executed remote index api on the source side, but it was not working.
Is this the correct way to use remote index api and Is it possible to use between v5.6 and v8.7
Thanks