If you have forgotten the wireless password of a network you have previously connected to you can view this by going into the wireless networks properties, but a simple command line utility also do this for older connected networks.

View wireless network profiles

netsh wlan show profiles

Show passwords in clear text

netsh wlan show profiles name=[profile name] key=clear

For more

Using Netsh Commands for Wi-Fi Management in Windows 10 | ServerWatch
https://www.serverwatch.com/guides/using-netsh-commands-for-wi-fi-management-in-windows-8/