Problem updating frimware.  

Problem updating frimware.

Hello, I am currently facing a problem of not being able to Update the firmware of my PRUSA MK3S printer ... 
the problem is with the COM3 port, which I cannot change from the "Device Manager ----> COM Ports" window. / LPT. When I try to go to Properties, it does not give me the option to enter the port settings.
 The error it shows me is the following:
 "avrdude-slic3r -v -p atmega2560 -c wiring -P COM3 -b 115200 -D -U flash: w: 0: C: \ Users \ dMihawkCL \ Desktop \ COVID 2020 \ 3D Printer \ prusa3d_fw_MK3S_3_9_1_3518.hex: iavrdude-slic3r: Version 6.3-20160220-prusa3d, compiled on Mar 21 2020 at 12:45:57 Copyright (c)
 2000-2005 Brian Dean,  http://www.bdmicro.com/  Copyright (c) 2007-2014 Joerg Wunsch Using Port: COM3 Using Programmer: wiring Overriding Baud Rate: 115200avrdude-slic3r: stk500v2_recv (): timeoutavrdude- slic3r: stk500v2_getsync ():
 timeo ut communicating with programmeravrdude-slic3r: 
Could not open port: COM3avrdude-slic3r done. Thank you."



I have looked for a way to be able to change the port, I even tried to use another computer, where if I could change the ports from the "Device Manager" window, I managed to change the port to COM6 or COM4, ​​but when loading the new firmware, I return to the same error described above ...
 the printer is new as a package, I am trying to update the firmware since the LCD screen does not give me an image, having everything well connected as the manual says.