No, the Schedule 8812 for 2018 in not used for your 2019 tax filing.
The Schedule 8812 is used to calculate and report the portion of the Child Tax Credit (CTC) that is "refundable", which means you get that portion of the CTC even if you don't owe taxes.
If you have a refundable CTC for 2019, your tax return will include a 2019 Schedule 8812.
This TurboTax article on IRS Form 8812 provides more details.