Question: can malwarebytes be run from a usb drive?
Answer: Copy the "Malwarebytes" folder to your USB drive, then delete the contents of the "Logs" and "Quarantine" folders that are inside the "Malwarebytes Anti-Malware" folder on the USB drive. Go to the PC that lacks Internet or is in Safe Mode. Install Malwarebytes from the mbam-setup if you haven't yet.