This is the gadget that I use in conjunction with a piece of software called “Spin it Again” to digitise my vinyl albums.
The Behringer UCA 202 is a USB soundcard with 4xRCA sockets that connect to the Tape Input & Output sockets on your hi-fi. Having connected it up anything that can be played via your hi-fi can be recorded to your PC.
It also has a S/PDIF optical output if required.
Also available is the Behringer UCA222 which is a more recent and slightly more expensive version. Both devices come with a vast range of free audio software that can be used to record your music etc.