If the children do not have Social Security numbers or ITIN's then you cannot claim them as dependents. Another thing---you do not mention your own immigration status. There is a chance you should not be using TurboTax, so you need to determine that before you proceed further with filing a tax return.
NON RESIDENT ALIEN
If you are a non-resident alien, your return must be filed on Form 1040NR, which cannot be prepared using TurboTax. You can use TT’s partner, sprintax:
https://www.sprintax.com/non-resident-alien-tax-1040nr-turbotax.html