DO NOT use online forms! Hire an attorney in the state where you intend to/do reside or in MO if that is where you own property. Most of your work can be done by email. Best wishes on for a happy and healthy child.
Even though you do not currently live in the USA, do you have a state that you use for legal residency purposes? That would be the state you can use. Generally forum shopping is frowned upon by the courts. Do not relay on online forms. They make the user feel they have a complete plan but since you won't know what is important to consider for your family, and no lawyer is there to help flesh out the issues, they can leave you in worse shape than having no plan at all.
You should not use online forms. You would normally have an attorney in the state that is your official domicile prepare the documents. You may also need to prepare a will or similar document for the country where you reside, especially if you own any land there.
First, online forms should not be used. A will should be prepared by an attorney who knows the requirements of making a valid will. If you make an online will and it is not valid then your estate would go by intestate succession, which may not be what you want.
The fact that the property is in Missouri does not mean that you need to make a will in Mo or even use a Mo lawyer. I recommend that you retain a lawyer in the state that you declare to be your domicile.
Nothing in this response is legal advice, nor does this response create an attorney-client relationship. It is for educational and informational purposes only.