I am trying to reinstate our library after upgrading server to Debian 8.5 with Plesk 12.5 panel,

I follow the instruction provided here

https://wiki.koha-community.org/wiki/Koha_on_Debian

I have done the steps, but

Install the Database

If you are planning to run MySQL on the same server that Koha is on, then run:

 $ sudo apt-get install mysql-server

I am assuming that we have already have mySQL server so I do not need this.

When I run this

# sudo koha-create --create-db library

I get

User library-koha already exists.

​I have not created user yet and this is a fresh install.

I do not see /etc/apache2/sites-enabled/library.conf​
​and I do not see 
/etc/koha/sites/library/koha-conf.xml
​Is there any solution to this please? How can I totally remove Koha and do a fresh start?