What does it mean "Your project must have at least three scripts total"? Does it mean three structure of "When GREEN_FLAG clicked and so on..."?
according to http://wiki.scratch.mit.edu/wiki/Script:
A script is a collection or stack of blocks that all interlock with one another. The blocks and their order are very important, as they determine how sprites interact with each other and the backdrop. Sometimes, comments are attached to scripts to explain what certain blocks do and what the script's purpose is.
In scratch, scripts are the colored blocks which have written command on it. You have to use it to move your sprite ( i.e the character ). The blocks get joined as soon you take them close. In your project it means you have to use at least three scripts ( i.e blocks) to make your project, to make your character move.