Factory reset dell computer

Which one of these two methods will work to restore a computer to Windows 10 factory setup and can I do it without connecting to the internet. My father was scammed and had some software installed by an "online repairman" so I'd like to start fresh and am hesitant to connect to the internet until we clean off whatever they installed.
1. Click Start , then type "reset".
2. Select Reset this PC (System Setting).
3. Under Advanced Startup, select Restart now.
4. At the Choose an option screen, select Troubleshoot.
5. Select Factory Image Restore.
6. Follow the on-screen instructions to complete the reset process. This will take some time and your computer will restart.

Restart your computer by clicking Start > arrow next to the Lock button > Restart.

As the computer restarts, press the F8 key until the Advanced Boot Options menu appears on the screen.

Note: You must press F8 before the Windows logo appears on the screen. If you press F8 after the Windows logo appears, the Advanced Boot Options menu will not appear on the screen. If you do not see the Advanced Boot Options menu, restart the computer, and then repeat this step until you see the menu on the screen.

Press the Down arrow to select the Repair Your Computer option on the Advanced Boot Options menu, and then press Enter. Select your language settings and then click Next.

Log in as an administrative user, and click OK. Then click the Dell Factory Image Restore option.

In the Dell Factory Image Restore window, click on Next. Check the box that reads Yes, reformat the hard drive and restore system software to factory conditions, followed by Next.

The computer will now restore to its default factory settings. Once the restore operation is completed, click on Finish to restart your computer.