Get the draft order id or the metafield

I ve created a private app to show a datepicker in checkout , and it also updates the metafield needed to the deliverydate. Issue is When a draft order is created, it too have a delivery date metafield and I need to get this from the app when the user is sent the order confirmation email and wants to checkout, so that I can get the draft order metafield and then update the order metafield respectively. Is there a way i can get the metafield of the draft order in the checkout page? Im using ui-extensions-react .