How to find givien index by name in PostgreSQL
As a horse_with_no_name provided, you can search the pg_indexes meta-table to find an index by name with the query:
SELECT * 
FROM pg_indexes 
WHERE indexname LIKE '%NameOfIndexYoureSearchingFor%';

Regarding your second question in the comments on how to delete an index in PostgreSQL, you can script it out with a query like this:
DROP INDEX NameOfIndexYouWantToDrop;

PostgreSQL documentation on DROP INDEX for more information.