instruct him, hit him with strokes when he does it. and let him know its not good

Easy, make u sure you take him back to the store and request to speak to a manager informing him what your son took the item without your consent...then if u get a good manager they would scare him half to death.

No, that's all wrong! He's 6 years old, he doesn't, punishing him will make things much worse. I recommend you to read a book from A.S. Neill called Summerhill - A radical approach to child rearing. I personally don't agree with everything he wrote, but it makes you think and be a better parent. I hope you will read it...
I'm Jana from Serbia by the way...

Sorry,
'he doesn't'- is an error :)

Talk to him about what he did but don't get angry. Let anger show as dissapointment. Spend quality time with him.

look!!!take from him things that he loves as a punishement then talk with him about it!!that it is wrong and not good !!!make him regret it ...then give him back his staff..keep an eye on him !!always and watch his behaviour then you will know his needs and he will not steal again.