Windows 7 support will end on January 14, 2020. Link to MS article.
In most cases Windows 7 can be updated to Windows 10 by downloading the update tool.
Before taking the plunge you would be advised to make a backup either locally or on the many cloud options available. But having done that your pc will probably keep all your data, photos doc’s etc. You also need to have licence numbers and installation disks or installation files for any software you may have purchased. A failsafe method would be to buy a Solid state drive and use that for your new installation leaving your old drive to go back to if you find something important missing. SSDS and extra ram are available from Crucial UK who also provide a scanner which gives you recommendations for your pc.
What does end of support mean for me?
After January 14, 2020, if your PC is running Windows 7, it will no longer receive security updates. Therefore, it’s important that you upgrade to a modern operating system such as Windows 10, which can provide the latest security updates to help keep you and your data safer. In addition, Microsoft customer service will no longer be available to provide Windows 7 technical support. Related services for Windows 7 will also be discontinued over time. For example, certain games such as Internet Backgammon and Internet Checkers as well as Electronic Program Guide for Windows Media Center are scheduled to be discontinued in January 2020.