Moving wordpress site

Goodmorning,
Hopefully someone can help me out with the following.
I recently received the SQL database of a wordpress site and the content of the site. However the previous provider didn’t provide me with the wp-config.php files etc. He told me that we need to reinstall wordpress and had to import the database. That being set and trying for hours I just can’t get it to work. The version of the site is 3.3.2 and I download the latest 3.6 ( not sure if it matters ). Those are the steps I followed:
1- import database in phpmyadmin
2- Install wordpress and link to database.
( error pops up that there is already a database )
3- Then I copied some content to the ftp location ( not sure what has to go where ).

When I then login I get an error in index.php on line 3 stating the get_header function is incorrect ( undefined ).

I know that I am messing it up completely but I just don’t know of how to achieve this.
Can anyone please provide me the answers on the following questions:
– Do I need to install the same version or will the newer version also work?
– Which data goes where as I have the following folders: Plugin, theme
The theme folder contains a folder named the name of the company and also a .ds_store file. In the company names folder I see a lot of files like:
* admin
* css
* functions
* images
*includes
* js
* scripts
* secondary_search_manufactures
404.php
archive.php
index.php
styles.css
etc.

Also if I need to download the same version as the previous holder where do I download this one ( v 3.3.2 )?

Please don’t direct me to other sources as I already browsed the internet for help but I don’t get it. I do know of how to import the database I just don’t know the correct steps and to place which data where.

** Ps.: I will install wordpress on the root of the website so not within folder ( like: https://www.domain.com/wp-admin ).