The first thing you should check is to see if your PC will support an upgrade to the latest operating system. If not you’re looking at a new PC.
If it WILL support an upgrade BACK ALL YOUR DATA UP BEFORE ANYTHING ELSE! I can’t emphasize this enough. Once it’s backed up (to an external drive, Google drive, Microsoft OneDrive, etc.) you can start the upgrade.
The above is a condensed version of the process and I know it will be confusing to you but the main thing is to make sure your machine will support the upgrade first.