To check your free disk space, click on the Folder icon on your task bar to open a Windows Explorer window.
Click This PC in the left hand column
Under the Devices and drives section, you should see your Windows 10 (C:) drive with the free space listed.
If you are verifying your free space so you are able to upgrade your computer, you will need 20 GB of free space to upgrade. Having too little space will cause many problems may make your computer unusable.
If you don’t have enough free space, there are two options
Alternatively, you can connect an empty USB flash drive with at least 8GB of storage space that Windows 10 will detect and use as temporary storage to perform the upgrade. This will DELETE any data you have on that drive, so be sure that you do not need any of the data on that drive before using it to upgrade your operating system.