Does the Ender 3 need an 8 pin mini USB or 5 pin, or no difference?
The ender 3 follows the USB standard for a USB-2.0/2.0 revised 5 pin USB-Mini-B.

To prove, a picture of it. Left, you can clearly count the 5 pins that conform to the standard.



as a side note: There is no 8 pin USB-Mini - Mini has the T-shape. In fact, there is not even a USB standard conform plug that has 8-pins! The standard allows only 4, 5, 9, 11 and 24 pins