affecting code configuration easy example help medium option page price product reach screen selected values variants

How can I change the product price based on the option values like small /medium/large? Is there some easy code that can do that... thanks....

You need to use price affecting variants for that. Please see "variants" section in the help page.

The example is given in the product configuration itself. You will reach that screen once you have selected "price affecting variants" in product configuration.