My employer reimbursed my meals by 1,648 but there is nothing in box 12 for it how/where do i report it?

Probably nowhere.

In most cases, the employer does a tax-free reimbursement under an "Accountable Plan".  That is not taxable, and there is nothing to enter on your tax return.

In the event the employer did add it to your taxable income (reimbursed under a non-accountable plan), the deduction for such things are no longer deductible on the Federal tax return (but some States may allow it).