No, you can't use pgAdmin on a Oracle DB because it won't support it. By default, the pgAdmin application was developed to be used with the PostgreSQL database only. It doesn't have support for other versions.
You can check this information on the following website: https://www.pgadmin.org/
There is also a documentation page provided by the developers where you can learn about it: https://www.pgadmin.org/docs/
