Modal dialog in WPF

Here is my problem: I am moving the application from Windows Forms to WPF, but I am completely new in WPF technology.

I was lucky that the creation of the tape also allowed me to add some elements to it, but now I'm struggling to create a modal dialogue.

How can i achieve this? I have already created the entire dialog design, but I can’t open it as a modal window.

Also, since this application should be developed as part of the MVVM template, where can I put this code? According to what I read, this code should be placed in the view class, am I correct.

Thanks in advance.