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

See the instructions in Change your Apple ID country or region - Apple Support

Regarding the balance, see the following from that same link:

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.

Buy something more expensive and pay the balance with a credit card or contact iTunes Support and ask them to zero balance your account. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.  You may need to pick a problem that is slightly different than yours to get a chat option.  

iTunes Support

iTunes Support – world wide