@TurboTaxVanessaIA right, see below.
Also, Alimony is not deductible for any court order that is signed after December 31, 2018. That's part of tax reform. While your separation order may have been signed in 2018, it is not clear to me whether a final divorce, that converts the separation order to a divorce order, will count as resetting the date on the order, making the payments not alimony after the date of the final divorce. This is also a matter that you will need to review with a professional.
"For payments required under divorce or separation instruments that is executed after Dec. 31, 2018, the new law eliminates the deduction for alimony payments. Recipients of affected alimony payments will no longer have to include them in taxable income.
This TCJA treatment of alimony payments will apply to payments that are required under divorce or separation instruments that are: (1) executed after Dec. 31, 2018 or (2) modified after that date if the modification specifically states that the TCJA treatment of alimony payments (not deductible by the payer and not taxable income for the recipient) now applies."
What I think this means is, that if you have an order signed in 2018, converting to a divorce in 2019 will count as a modification. You have the option of saying "the TCJA does not apply and these payments are still considered deductible alimony". If the order does not say that, then the alimony becomes non-deductible and non-taxable as of the date of the conversion to a final divorce.
This could be a matter for negotiations, you might consider agreeing that the payments are not deductible alimony in return for a reduction in the payment. This would simplify both you and your ex's tax position.
As I said before, you should probably consult a professional.
