I can't find the server side script. Please can you help?

Server side scripts are just scripts, the icon that is the blue scroll. Client side scripts are LocalScripts, the scroll icon with the player on it.

This article goes more in depth on how to get to the sever, and even back to the client. [https://developer.roblox.com/articles/Roblox-Client-Server-Model]

I'd also recommend to read up on RemoteEvents, RemoteFunctions, BindableEvents, and BindableFunctions which can be used to get information from the server or client, and bring it back to another server or client. https://developer.roblox.com/articles/Remote-Functions-and-Events