How to update from Mojave to Ventura

While it can be done, it is a very big jump (4 generations of macOS). I suggest upgrading in two steps, going at least to Catalina first (or maybe Big Sur), and from there upgrade to Ventura.

FWIW, if it were me, I would back up all my data to an external drive, then wipe the system drive, reformat it as APFS and install Ventura from scratch instead of doing any upgrades. Of course, that would also mean reinstalling the applications you are currently using ... but you may have to do that anyway because you probably have apps on your Mojave system that won't run in Ventura.

You should be able to upgrade directly. Be aware Ventura is 64bit only so older 32bit apps that would run on Mojave will no longer work. Check for them with Go64. Also, be sure to back up first.