to the same folder as the forum so the folder structure looks like

did you add any plugins to the plugins folder?
They need to be downloaded separately, plugins folder should look something like below, depending what plugins you add
You may also need to do a recycle to pick them up once added, Admin Menu | Reset App Pool

what plugin did you add ?

did you apply any dbs files for the plugins? The forum checks for existence of tables in the database to decide if certain plugins have been installed

Question, looking at the folder structure within plugins.zip. Under Scripts, there is a sub folder called pluginjs, (which contains the scripts). Should these files go in the corresponding folder, i.e. scripts, content etc, and not just move the pluginjs/plugincss folders. If you open up the zip files, you'll see what i mean.