Assuming that the 'number' is a content control titled 'Number' then the following should save the document in the user's documents folder. with the name e.g. 12345-20191112.docx
Sub SaveForm()
Dim strPath As String
Dim oCC As ContentControl
strPath = Environ("USERPROFILE") & Chr(92) & "Documents\"
Set oCC = ActiveDocument.SelectContentControlsByTitle("Number").Item(1)
If oCC.ShowingPlaceholderText = True Then
Beep
MsgBox "Complete the missing information!"
oCC.Range.Select
GoTo lbl_Exit
Else
ActiveDocument.SaveAs2 FileName:=strPath & oCC.Range.Text & Format(Date, "-yyyymmdd") & ".docx"
End If
lbl_Exit:
Set oCC = Nothing
Exit Sub
End Sub