SOFTWARE UPDATE
how do I update my software?
MacBook Pro 13″, macOS 10.13
An update is a point release (e.g. 10.13.4 -> 10.13.6) and an upgrade is major release (10.13.6 -> 10.14.6). If you actually want to perform an upgrade, then view How to get old versions of macOS using the Safari browser.
Once you have the market introduction year of your Mac from menu : About This Mac : product description including date in parenthesis — you can then compare the date of your Mac with the hardware requirements from that link, and then gain access to the Mac App Store download page.