What charger do I plug this beats cord into?
I have never seen the charging cord that came with my new Beats Flex. I don’t know what to plug it into.
That is a USB-C cable. If you don't have any USB-C power adapters or computers with USB-C, the following is one option: https://www.apple.com/shop/product/MHJA3AM/A/20w-usb-c-power-adapter