It depends on your current MacBook models there are some models that can't able to upgrade/update with the latest version.

See the list of compatibility from these links below.

- https://eshop.macsales.com/guides/Mac_OS_X_Compatibility
- https://everymac.com/systems/by_capability/maximum-macos-supported.html

Then look for your model and let's see if your device is compatible to upgrade to the 10.13 or above version of OSX