Hi i want to change my iTunes account from US Store to Saudi Arabia Store and i want to reset My balance.

If you need to zero out your balance

You have 2 options

Have at least 1 other valid payment method and make 1 purchase or more purchase until you zero it out.

For the last purchase costing less than the cost of what you are buying some of it will be taken from your Apple ID balance, the rest from the payment method.

Or you can ask apple to remove it after buying something until you have less than the cost of a single item

Contact Apple for support and service - Apple Support

From:

Change your Apple ID country or region - Apple Support

Contact Apple Support

If you can't complete any of the steps, can't change your country or region, or you have less store credit than the cost of a single item, contact Apple Support.

Good luck!