You need to install Python 3.12 outside your virtual environment, then create a new virtual environment for Python 3.12 and install the necessary packages in it.* (Yes, you can have multiple different version of Python installed in your Windows system.)
(You don’t run Python in an virtual environment. You’re creating a virtual environment using Python to run Django.)
*Note: There are other ways of doing this, but this is typically the easiest and most straight-forward.