Most importantly, your current version of Windows is properly activated. Although Microsoft mentioned that Windows 10 will be completely upgraded and will even be installed on pirated and/or inactive copies of Windows, this plan will never be achieved, and of course you will need to activate a copy under the current deployment model.
To check if your copy of Windows 8 is activated, press Windows + W to boost the settings search, type "activate" in the search box, and open the "View if Windows is already activated" result. Or you can check the status of the machine under Control Panel -> System.
To check if your copy of Windows 7 is activated, click Start, right-click on the "Computer" option, and select the "Properties" command. The results window shows if your copy of Windows is activated.
After viewing, you can go to Microsoft to download: https://www.microsoft.com/en-us/software-download/windows10
However, you need to pay attention before starting. The update tool will find the correct version of Windows that you need to update. It determines whether your current Windows version is 32-bit or 64-bit and updates you to the same version. Even if your PC supports it, you cannot use the update tool to move from a 32-bit installation of Windows 7 or 8 to a 64-bit installation of Windows 10. If you are running a 32-bit version of Windows and you want to migrate to the 64-bit version, you must perform a fresh installation instead.
Video of Upgrade from windows 7 to windows 10:
Run the upgrade installer
When you are ready to upgrade, run the installer tool (named MediaCreationTool) to get started.
You will be prompted to upgrade your PC first, or create installation media for another PC. Select "Upgrade this PC now" to start the upgrade process and click the "Next" button. The tool begins to download the Windows 10 installation files. The time required depends on your Internet connection speed. We reduce to 100% in minutes with a fast cable connection, but if the connection is slow, you may observe the meter for a period of time.
When it finally finishes downloading and unzipping the installation media, you are prompted to accept the terms of the license agreement. Click "Accept" and the installer will perform the last update check before kicking you to the final confirmation page.
Follow the prompts to complete the upgrade. You will not be required to provide a product key, and when the upgrade is completed and you are connected to the Internet, you will have a digital license for Windows 10, which you can confirm by going to Settings> Updates and Security> Activation.