under help in menu bar not showing "check for updates

Given you're running Windows 10 there is a high likelihood you're running the version from the Microsoft Store. The current version is 12.9.4.102. Use Help > About iTunes to check which version you have. What issue is it that is prompting you to look for an update?

tt2

I can see it on my Windows 10 machine. It's third up from the bottom of the list, which contains fourteen items on the menu.

Here's a screenshot from my Windows 7 machine, but I've just checked, it's exactly the same as the one on Windows 10:

In what way does your list differ?

Did you install iTunes in Windows 10 from the Microsoft Store or using the traditional iTunes(64)Setup.exe file? It is possible the first version is updated differently, e.g. automatically with Microsoft Update.

tt2

For general advice see Troubleshooting issues with iTunes for Windows updates.

The steps in the second box are a guide to removing everything related to iTunes and then rebuilding it which is often a good starting point unless the symptoms indicate a more specific approach. When reinstalling right click on the downloaded setup file and use run as administrator. It may also help to temporarily disable any non-Microsoft anti-virus.

Review the other boxes and the list of support documents further down the page in case one of them applies.

The further information area has direct links to the current and recent builds in case you have problems downloading, or want to revert to an older version if the current one won't work properly for you at the moment. Links to the most recent builds are now at the bottom of the page.

Your library and device backups should be unaffected by these steps but there are links to backup and recovery advice should it be needed.

tt2