My Rpi3b + was running fine with raspbian, I followed the code from support website to change the boot to usb, I think it worked, but my usb was not right with the os.
How do I get the pi to go back to the micro sd booting ?
You will still be able to boot from an SD card.
The Pi3 will check for a boot SD card first, before booting from a USB device. If no boot SD card is found in 5 seconds, then it looks for a boot USB device. So even if the boot USB device is still connected, inserting an SD card will override it.