Since the code you gave here won't compile, it sounds like you're not actually even compiling and just trying to use the source code itself as a plugin.
The compiler turns source code into an actual plugin. You can run the compiler locally by getting it out of a SM release archive (spcomp or spcomp.exe depending on your platform; get the archive for the OS you want to run the compiler on, which may be different than what your server runs on). You can also use the web compiler at
https://www.sourcemod.net/compiler.php or asherkin's alternate tool, Spider, at
https://spider.limetech.io/.