Don't return a string, this was said 1000th times already, I am not sure why people keep doing this. It just stupid.
You have some natives called get_string/set_string, search for them. Also the loop looks silly, instead of it check if g_szModels[0] is the name that you get from the native(get_string) and use set_string with g_szModels[1].
Keep in mind that you are working with natives registered with style 0, so they don't pass the parameters. They only pass the plugin index and the param num. You have to use specific natives to get the params value(get_param/get_string etc).