So yes, support for Windows 10 ends in just over a month, and after that if you haven't upgraded to Windows 11 you'll see no more updates from Microsoft...not even for security fixes.
If you have a valid Windows 10 licence, (even if you got to Windows 10 from an even earlier version), you can upgrade to Windows 11 for free. Microsoft provide a handy tool called the PC Health Check...you may already have this on your computer, or you may need to download* it before you run it.
Either way, the steps to follow are in this article from Microsoft -> Check if a device meets Windows 11 requirements. The link to down load the tool is on this page if you don't already have it.
The most common 'issues' the checker will find will be related to either, (**jargon alert**), the Trusted Platform Module, (TPM), or UEFI/Secure Boot. So, what are these and how do you get them? Both are for computer security, and if your machine is relatively new they will be there, just possibly not switched on. For example, the machine I'm typing this one was first built in 2020 and those two things were there from the start.
Switching them on though involves going into the (**jargon alert**) firmware, (UEFI or BIOS), which is the bit that lets all the other bits of your computer talk to each other. When you start your machine up you can get into this by hitting a key repeatedly, often the Delete ('Del') key. There's normally a message on screen just after you switch on telling you what key to press but pay attention, it doesn't show up on screen for long!
There's a short support article from Microsoft here -> Windows 11 and Secure Boot that talks about UEFI/Secure Boot in a bit more detail, and provides links to the manufacturer websites for more help if you happen to have a Dell, Lenovo, or HP machine.
Once the PC Health Check says you are good to go, the simplest way to upgrade is to download* the Windows 11 Installation Assistant and follow the steps when you run it. You can find that in this article from Microsoft -> Download Windows 11. There are other ways to do it, and that article explains them, but the assistant is the simplest.
Whatever way you choose to do the upgrade, it is a VERY good idea to back up all your documents, photos, music, and other items just in case.
Of course, if all that seems way too technical or far too much effort, feel free to get in touch, I can help!
*NEVER download something from a website that isn't the official one of the manufacturer or supplier, or from a website that you absolutely trust! The links above point to the official Microsoft support articles, and these have the official download links in them.