If this is your database, then you better know what databases you have and why you have them.
One possibility is that you have lost control of your database, probably to cryptomining hackers (they do create databases with gibberish names).
You can delete the extra's, but the hackers will just keep on getting back in if you don't fix the underlying problem. You need to give good passwords to all your superuser accounts (and all non-superuser accounts too), block access to your database to all but white-listed hosts in pg_hba.conf, maybe block super-user access from all but localhost, as well as blocking access to 5432 on your firewall to all but trusted hosts. Any one of these might be sufficient, but you will be better off to do all 4 of these things.