In the table of VM instances, click the arrow by "SSH" in the row for your virtual machine, and click "Open in browser window"
When the window finally opens, run lsb_release -a. If all is well,
it should show you what version of Ubuntu you're running (hopefully
20.04). It should look something like this:
Congrats, you've created your first virtual machine with Linux installed! This is no small feat, and being able to do so in the future in an invaluable career skill.