ServerScriptService.MainScript:5: attempt to get length of local 'spawns' (a userdata value)
As you put no code at all, I'll just try my best guessing.
ServerScriptService.MainScript:5: attempt to get length of local 'spawns' (a userdata value) you most likely used string.len() to get the length of a string. If spawns is a userdata value then it can only be a TextBox, TextLabel, TextButton or StringValue. You'll need to add .Text or .Value to that. Correct me if I'm wrong, but I think that a userdata value is an object such as a part.