You might doubt that how Sony Playstation 4 controller used in Nintendo Switch? This video below show you how to achieve with 8bitdo USB Adapter for PS classic that also work in Nintendo Switch.
This usb adapter also can be applied to PS Classic too.
Find more information and user manual here : http://download.8bitdo.com/Manual/Receiver/usb_adapter/8Bitdo_USB_RR_FOR_PS_Manual.pdf
You may get your own via online store below:
Amazon (Global) = https://amzn.to/2T4LcEL
Shopee (Malaysia) = http://invol.co/cle3nv