I don’t have Windows10 so not 100% sure, but the pixhawk should be listed differently.
What other options do you have in the drop down list?
Also the baud rate is almost certainly wrong. - usually more like 57600 or 115200
Anyway, MP is connected to something as indicated by the icon on the far top right.
Click disconnect - wait until it shows disconnected icon -then click connect. The connection window should pop up. If it cannot talk to Pixhawk it will tell you after 30 seconds.
Then repeat above process but after icon shows disconnect state change baud rate and press connect again.
I had all my flight-controllers work on USB with either 57600 baud rate or 115200
→ Just noticed, you are connected just not talking for some reason. You can see this in the very top of your screen where it says " ArduCopter 4.2.2"
Disconnect USB cable. Wait a few seconds then connect it again.
See what Mission Planner does at the top right regarding the connection icon and also to the left if “Arducopter 4.2.2” is showing again.
You may have to click on the config tab / icon and see if initial settings are still there.
Also note this remark given in that link I’ve sent you:
If FMUv3 doesn’t work you might find updating the bootloader sorts it, both my clones (not MRo) were detected as FMUv2 but they had the fixed chip so with an updated bootloader work fine and are now detected as FMUv3. Qgroundcontrol can update it and has instructions if you google update pixhawk bootloader.
→ Only proceed with QGroundcontrol if above advice doesn’t work.