Troubleshoot Internet Problem

This is an emergency and I need help right now!!!!! I have a Dell Optiplex 755 Computer and at the back it has an internet Tecknet USB or it’s a USB Key or a USB chip or a memory stick - I don’t know but my computer has internet issues. I have Windows 10. It says the problem is that it’s not connected to the internet due to troubleshooting and it says it needs an Ethernet cable. I don’t need an Ethernet cable because I have an internet USB which can be plugged into the computer and I can use the internet and WiFi without an Ethernet cable but now the internet doesn’t work in my computer and it can’t search for any Wifi’s so it doesn’t work. As you can see, I have another computer downstairs and it’s connected to the WiFi with the Ethernet cable but my other one upstairs isn’t but it still works because it has an internet USB I guess and it came with it when my dad brought the computer for me on Christmas Eve. But now, the computer isn’t connected to the internet anymore. I don’t know what to do????????? And sorry it’s not an Internet Key.