With all plugged in assign each a drive letter of your choice using Disk management (leaving gaps if necessary for card reader slots).
Next time you reboot or plug in a drive it should keep the same drive letter. (USB drives must always be plugged into the same slot as when the drive letter was assigned.
I have a drive I have assigned as P: (Verbatim)
Internal drives C - H with G as DVD drive with even without drives I J K l M switch on if I power up the Verbatim drive it will always be assigned the letter P