There is Parallels Transporter, which should enable what you want. You need to run it first - before you get rid of the bootcamp partition (of course) - in Windows and using it "export" the Windows system/data to external drive. Then import to Parallels new VM.
Warning: often when I tried this, it failed miserably and nothing useful came out of a long procedure. However, it should work, costs nothing, so I would try it.
I would FIRST install Parallels, and move the bootcamp Windows system into the new Parallels VM and - only after proper testing - remove the bootcamp partition. This way you can go back and test everything if needed. In my experience, this procedure is prone to failures. Sometimes it all worked on second/third attempt (while doing the same steps, go figure...).