Plugins Folder Absolute Path

I recently installed WP 2.71 in the sub folder of my joomla site. After WP installation, I installed plugins. When I checked on the plugin, it did not show in the list, there was actually no list at all. So, I guessed the plugins foler pathway might be wrongly installed.

True enough, there was no plugins folder in the wp-content folder.
After using ftp, I noticed that was one plugins (the original for Joomla 1.59) folder under the root directory, and the installed plugins are residing inside now.

How do I change the wp—> plugins folder path to tell the installation to put in wp plugin folder instead of Joomla folder?

Thanks in advance. Please tell me specifically which file(s) to change and the absolute “path” for this to work.