What is the '1' app from the starup app?

You can check and delete it with the Autoruns utility:
https://learn.microsoft.com/en-us/sysinternals/downloads/autoruns

It seems the PC has malware installed. I don't see this app from my task manager.

“Startup Application” is usually the startup program for the Firefly Camera software. It may pop up a window when your computer starts up. If you need to solve this problem, you can find and disable “Startup Application” by right-clicking on the taskbar, selecting Task Manager, and then finding and disabling it in Startup Items.

Disable the app from startup and reboot your computer.
P.S. Did you install any suspicious app recently?

reboot the computer and see if the task name disappears from the computer.