Sorry to be the one to tell you this my guy,
unfortunately the WiFi is integrated into the phone’s logic board. Although if you want to save your phone then my advice would be to backup your phones data to your computer and replace the logic board on the old phone. Their isn’t a guid on iFixit ***yet***, but their is a good guide you can follow [link|https://vrm24.com/instructions/how-to-disassemble-xiaomi-redmi-note-9/|here].