Here a USB 3 external hard drive can be seen placed as far away as possible on a desk from the Bluetooth mouse
If your USB 3.0 device needs a cable to sit between the computer and the device (many do, for example external hard drives) make sure that the cable is fully extended with the device as far away from the computer as possible.
Also position the USB 3.0 device/s as far away from your Bluetooth devices as possible. For example; if you have a hard drive, don't have it sitting next to your Bluetooth mouse or keyboard but instead in the opposite direction ideally behind the computer.
Here a USB 3 external hard drive can be seen placed on the oposite side of the laptop to a Bluetooth mouse. The USB 3 cable is also extended fully and in a direction away from the laptop and Bluetooth mouse
If there is a USB 3.0 hub between the end device and computer also ensure that this and any cables attached to it are also as far away as possible from your Bluetooth devices.
If the device was supplied with a particularly short USB 3.0 compatible cable then you may want to replace it with a longer one. USB 3.0 cables can be found up to 3 meters in length so this should give you plenty of distance to better separate the device. Make sure that you buy a quality shielded USB 3.0 compatible cable.