Question

explain how you could use a spring a ruler some standard masses and some graph paper to find the waight of an unknown object

Answer 1

You place a standard weight on the spring and measure how much the spring is pulled down with the ruler. Continue with the other standard masses.Then graph the spring distance on the y axis against the standard weight used on the x axis. Then place the "unknown object (see note below)", measure the deflection of the spring, and read the weight of the object from the graph.
NOTE: I think you meant to determine the unknown weight of an object. If it's an unknown object I don't think determining its weight will tell you what it is.