Google ``useful linux commands" and you will see many online resources for newbies, like this one.
Google ``How to XYZ Linux'' if you want to know how to XYZ. XYZ can be, e.g, how to delete a folder, how to view existing USB devices, and so on.
After you type in a command, Ubuntu often provides useful hints if it cannot find it. For example, it may suggest the command line for installing the missing command. So if your attempt was not sucessful, read the feedback carefully :-)
Useful ways to work with a commandline utility
utility > temp.txt.
>will delete temp.txt and create a new one if it already exists. If you would like to pend the output to an existing ile, use
>>instead. Read more about IO redirection here.
sudo apt-get install packagename
sudo apt-get updateand
sudo apt-get upgrade. See here for the difference between update and upgrade.
apt-cache show packagenameto view information about a package
Use multiple utilities