The Standard toolbar has not moved. That area where those buttons are by default is called the "menu bar" as described in this help topic: 2018 SOLIDWORKS Help - Menu Bar
You cannot dock an entire toolbar there, but you can put buttons there by using Tools, Customize, Commands. The default setup has a combination of flyout toolbar buttons and regular toolbar buttons there.
However, if those buttons have disappeared without you doing anything, then your Microsoft registry where all the SOLIDWORKS settings/user interface definition is stored probably got "damaged' somehow. And if that is the case, there will likely be more problems than just those buttons being missing. Do you have a backup of your settings that you saved using the Copy Settings Wizard? If so, restoring from that is the best course of action.
Thanks Jim. I had (luckily) backed up my setting earlier this month. Restoring was the only solution.