Dear Mohammad,
In order to get the list of organizations using ReliefWeb API, you can use the /sources endpoint.
So, the final; query would be:
The query returns 10 results by default, use the limit parameter, to increase the number of results. If there are more than 1000 results, you must need to do several queries for each page using the "offset" parameter.
Are you able to share what is the purpose of this research?
Let us know if you have further questions.
Best,
Miguel Hernandez
ReliefWeb Product Manager