I need to make this textbox not move

Rules of WPF:

❌ Avoid the WPF Designer to eliminate a category of confusing bugs
❌ Don't rely on Margin as the primary tool for layouts
❌ Avoid writing UserControls or subclassing to extend a default control -- use Behaviors instead (Microsoft.Xaml.Behaviors.Wpf)

✅ Write XAML by hand and autoformat with "Ctrl K,D" or XAML Styler
✅ Rely upon XAML Hot Reload to design your app's UI at runtime
✅ Use layout controls (Grid, DockPanel, etc) to support proper resizing
✅ Use data binding to eliminate glue code and state synchronization issues
✅ Use collection controls and DataTemplate to dynamically create lists of controls
✅ Learn MVVM to create maintainable apps
✅ Use the Dispatcher to update controls from non-UI threads
✅ WPF's default controls can be easily modernized via $wpfuilibs
✅ Include relevant XAML, code-behind, and ViewModel code for questions when possible

Rules of WPF:

❌ Avoid the WPF Designer to eliminate a category of confusing bugs
❌ Don't rely on Margin as the primary tool for layouts
❌ Avoid writing UserControls or subclassing to extend a default control -- use Behaviors instead (Microsoft.Xaml.Behaviors.Wpf)

✅ Write XAML by hand and autoformat with "Ctrl K,D" or XAML Styler
✅ Rely upon XAML Hot Reload to design your app's UI at runtime
✅ Use layout controls (Grid, DockPanel, etc) to support proper resizing
✅ Use data binding to eliminate glue code and state synchronization issues
✅ Use collection controls and DataTemplate to dynamically create lists of controls
✅ Learn MVVM to create maintainable apps
✅ Use the Dispatcher to update controls from non-UI threads
✅ WPF's default controls can be easily modernized via $wpfuilibs
✅ Include relevant XAML, code-behind, and ViewModel code for questions when possible

        <StackPanel Orientation="Horizontal" VerticalAlignment="Center" Margin="10,0,0,0">
            <Label Margin="25">Select account</Label>
            <ComboBox Name="AccountBox" Width="140" Height="30">
            <TextBlock Height="40">
                <Run Text="Password: "/>
                <Run Text="{Binding ElementName=AccountBox, Path=SelectedItem}"/>
            </TextBlock>
            <TextBlock x:Name="AccountPassword" Width="300" Height="40" FontSize="30"/>
        </StackPanel>

        <StackPanel Orientation="Horizontal" VerticalAlignment="Center" Margin="10,0,0,0">
            <Label Margin="25">Select account</Label>
            <ComboBox Name="AccountBox" Width="140" Height="30">
            <TextBlock Height="40">
                <Run Text="Password: "/>
                <Run Text="{Binding ElementName=AccountBox, Path=SelectedItem}"/>
            </TextBlock>
            <TextBlock x:Name="AccountPassword" Width="300" Height="40" FontSize="30"/>
        </StackPanel>

    <Grid>
        <StackPanel Orientation="Vertical" Margin="10">
            <TextBlock Text="Select account" />
            <ComboBox Name="AccountBox" Width="140" Height="30" HorizontalAlignment="Left">
                <ComboBoxItem>Something</ComboBoxItem>
            </ComboBox>
            <TextBlock Height="40">
                <Run Text="Password: "/>
                <Run Text="{Binding ElementName=AccountBox, Path=SelectedItem}"/>
            </TextBlock>
            <TextBlock x:Name="AccountPassword" Width="300" Height="40" FontSize="30"/>
        </StackPanel>
    </Grid>

    <Grid>
        <StackPanel Orientation="Vertical" Margin="10">
            <TextBlock Text="Select account" />
            <ComboBox Name="AccountBox" Width="140" Height="30" HorizontalAlignment="Left">
                <ComboBoxItem>Something</ComboBoxItem>
            </ComboBox>
            <TextBlock Height="40">
                <Run Text="Password: "/>
                <Run Text="{Binding ElementName=AccountBox, Path=SelectedItem}"/>
            </TextBlock>
            <TextBlock x:Name="AccountPassword" Width="300" Height="40" FontSize="30"/>
        </StackPanel>
    </Grid>