How to autosize path to grid container in WPF - wpf

Question

In WPF application, text is going out of its path as per screenshot.Please suggest how can we autosize it according to resolution/window size.i tried to set few property but did not help.
<Grid Grid.Row="0" >
<Popup x:Name="popLines"
PlacementTarget="{Binding ElementName=btn}"
Placement="Relative"
IsOpen="False"
Width="750"
ScrollViewer.CanContentScroll="True"
AllowsTransparency="True"
StaysOpen="False"
PopupAnimation="Scroll"
HorizontalAlignment="Left"
VerticalAlignment="Top"
HorizontalOffset="-190" VerticalOffset="0"
ToolTip="Approval Screen Help">
<Grid Margin="10">
<Path Fill="LightBlue" Stretch="Fill" Stroke="LightBlue"
StrokeThickness="3" StrokeLineJoin="Round"
Margin="0" Data="M130,154 L427.5,154 427.5,240.5 299.5,240.5 287.5,245.5 275.5,240.5 130,240.5 z">
<Path.Effect>
<DropShadowEffect BlurRadius="12" Color="Black" Direction="315" Opacity="0.8"/>
</Path.Effect>
</Path>
<Grid Margin="10,5,10,5" HorizontalAlignment="Stretch" VerticalAlignment="Top">
<Grid.RowDefinitions>
<RowDefinition Height="10"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Button Style="{StaticResource XBtn}" Click="btn1_Click" Grid.Row="0" HorizontalAlignment="Right" VerticalAlignment="Top"/>
<TextBlock Grid.Row="1" TextWrapping="Wrap" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"
Text="{Binding ApprovalScreenHelp}">
</TextBlock>
</Grid>
</Grid>
</Popup>
</Grid>