are you trying to run this plugin?:
http://forums.alliedmods.net/showthread.php?p=1559567
If so uploading the files on the right spot and changing map should do the trick
plugin_load is for loading valve server plugins I believe they are called (metamod, mani vsp and eventscripts)
"meta load" and "meta unload" is for loading/unloading metamod plugins manually which shouldnt really be needed as they are usually run on server start or mapchange anyway.
then there is
sm plugins load
sm plugins unload
sm plugins reload
for sourcemod to load unload and reload. which is probarly what you should be using for the above plugin though it should start on its own after a mapchange or server start.
also you can check if its loaded by using "sm plugins list"
Hope this helps a bit.