Any existing Cubase 11 LE users are entitled to upgrade to a later Cubase LE version for free. You should have received an email from Steinberg that outlines the steps to update.
More information from Steinberg about this can be found here: https://helpcenter.steinberg.de/hc/en-us/articles/4448449036946-Cubase-LE-AI-12-free-updates-for-users-of-previous-versions-