Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, the Canon Pixma MG300 series including the 3520 are wireless printer and as such, the USB port is not functional. This is as stipulated in the overview of the features of this particular model as may be viewed in Item # ***** HERE; "...A printer connected to the USB port of your Mac, PC, AirPort Base station, or Time Capsule is not supported..."
I realize that the above information may perhaps be not what was expected. Unfortunately, it is a design imposed limitation; sorry for having to be the bearer of bad news.