How to copy a video file and MP3 to your mobile phone

Example QRcode

I still have one of these old bricks, a mobile phone without a shiny display, just a mouse cinema, not one of these new smart phones. But I still use it quite a lot, I love to play Mahjongg (the real traditional chinese one), listen to music or my spanish lessons and sometimes I even watch some short clips. The problem I often face is how to get the files I want to my mobile