How to get the viewmodel data into another viewmodel

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WPF

MVVM

In Screen1 : I'm having 2 textbox and a button. once i click into a button, data should comes into Screen2 which is having a datagrid. and display the value of 2 textboxed into a datagrid coloumns.

In Screen 3 I have combobox and a button , when i click on the button the combobox data should get displayed in datagrid in screen 2 along with 2 textboxes.


Can anyone tells me how to do it?

What I have tried:

Screen 1 VeiwModel
 private string _txtNumBox;
        public string TxtNumBox
        {
            get { return this._txtNumBox; }
            set
            {
                if (value != this._txtNumBox)
                {
                    this._txtNumBox = value;
                    this.NotifyPropertyChanged(TxtNumBox);
                    getResult();
                }
            }

        }

        private string _txtRCBox;
        public string TxtRCBox
        {
            get { return this._txtRCBox; }
            set
            {
                if (value != this._txtRCBox)
                {
                    this._txtRCBox = value;
                    this.NotifyPropertyChanged(TxtRCBox);
                    getResult();
                }
            }
        }    

Screen 2:

public class FinishedManualSelectionVM
   {
       FinishedManualPrintingVM fmpVM = new FinishedManualPrintingVM();
       public FinishedManualSelectionVM()
       {
           getGridDatafromScreen2();
       }

       public void getGridDatafromScreen2()
       {
           // var anum = fmpVM.TxtNumBox;
           var anum = fmpVM.TxtNumBox;
       }

   }