My MacBook high Sierra doesn't have the latest software update.

christinaray wrote:

macOS High Sierra Version 10.13.6 (17G14042

Just knowing that your machine runs High Sierra isn't enough to tell us whether you can upgrade macOS. That's why I asked for the model name and hardware release date.

An example of a model name and hardware date would be MacBook Pro (13-inch, Late 2011). For that machine, High Sierra is the end of the line. A MacBook Pro (15-inch, 2017) is old enough that it can run High Sierra – but for it, Ventura is the end of the line.

What does it say in  > About This Mac about your Mac's model name and hardware release date?

That will determine how far you can upgrade macOS – if you can upgrade it at all.