Hello,
The message looks legit, and it seems you're on Windows 10 V1809, support for which will end on may 12, 2020.
I recommend you to upgrade to latest version atm i.e. V1909 via ISO file.
Refer this step-by-step guide:
https://www.kapilarya.com/how-to-upgrade-to-windows-10-using-iso-file
Let us know if this helps!
Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.