Here. Try This
For I = 0 To dgv.RowCount - 1
If dgv.Rows(I).Cells(1).Value.ToString = "Your Search Text" Then
TextBox1.Text = dgv.Rows(I).Cells(0).Value.ToString
End If
Next
In IF Condition, Change the value of cell to column Index from where you have to search your text value and then assign the correct cell value from that row to text box.
Hope this helps.