Hello Richard,
Since the 4 pin on your motherboard is 12V, and the digital RGB LED of your fan is 3 pin, 5V. The volt is different. So there is no adapter to make 4 pin compatible. But you can use the DRGB controller BPTA-DRGBMFC-V2 to control the 3 Pin DRGB LED strip.
https://shop.bitspower.com/index.php?route=product/product&product_id=7822&search=CONTROLLER