Hi, @Gerald Ortiz Candela Welcome to Microsoft Q&A thanks for posting your question.
As per the documentation, the backup storage redundancy option, whether locally redundant or geo-redundant, can only be set during server creation. Once the server is created, you cannot change the backup storage redundancy option.
If you need to change the backup storage redundancy option, you will need to create a new server with the desired redundancy option and migrate your data to the new server.
https://learn.microsoft.com/en-us/azure/postgresql/single-server/concepts-backup
Regards
Geetha