Hi, two intruders were using my pc were caught by my mcafee as "192.168.1.3 unknown device"

If the wireless connection is turned off in the router, the ‘unknown device’ must have been connected by wire. Do you have devices like a network hard disk or an Xbox? If so, one of them will be IP address 192.168.1.3 that McAfee blocked.

Are you sure that wireless access has been turned off in the router?

To check which computers (computer names) are connected to your router, you can look at the router’s configuration pages or for a simple list, open a Run window (Windows Logo key+R), type cmd and press Enter, now type NET VIEW (the capitals are for clarity only) and press Enter.

To see more information, using your wired computer access the router’s set up details. This is done in a home network by typing 192.168.x.y into a browser’s Address bar. The values of x and y depend upon the make of router. If you don’t know the values, open a Run window (Windows Logo key+R), type cmd /k ipconfig (note the two spaces), press Enter, make a note of the Default Gateway address and type it into the browser’s Address bar. When asked for the user name and password, type the default values, often admin and admin  (if they are not known, look in the router’s user manual).

Once you have gained access to the router, look for (usually) an Advanced section named DHCP Table or similar wording. This will show all connected (and expired) IP addresses that have been connected, together with their names.