Can't import dump database to PostgreSQL

Question

I'm using pybossa and PostgreSQL. My list of databases are like this:

I have a dump collection for pybosssa database named: pybossa-db-oct2-final.bak

I want to import it on the pybossa db. The problem is that I'm not so familiar with PostgreSQL. I checked this page https://www.postgresql.org/docs/9.5/static/backup-dump.html but there are some instructions only for compressed dumps but not for .bak files.

I tried like this:

pg_dump pybossa pybossa-db-oct2-final.bak

But this didn't work? I need help can someone help me, please?

Edit:

I tried this command:

 pg_restore -d pybossa /home/sagar/Download/sample_dbump

I get this:

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
    LANGUAGE = (unset),
    LC_ALL = (unset),
    LC_CTYPE = "UTF-8",
    LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
pg_restore: [archiver] could not open input file "/home/sagar/Download/sample_dbump
": No such file or directory

In this /home/sagar/Download/sample_dbump my file pybossa-db-oct2-final.bak is found, I used pwd command to define the path