Walmart does not offer cashier's checks however you can cash a cashiers check at Walmart's money center for a fee.
If you want a Cashier's check you'll have to go to the bank you have a checking or savings account with and have the bank issue a cashiers check using the funds in your account.
There is a fee for a cashiers check at your bank which can vary depending on who you bank with but the cashiers check fee ranges from $5.00 to $10.00 per cashiers check