Hey Diana, there is a little extra work to update between such a wide range of versions. Version 1.16.0 had particular changes you can learn more about here. Aside from that there is not an a single outline, so you should expect to hit some additional speed bumps. I would recommend referencing a fresh 1.30 site to be able to see what an end state should look like file name/location wise.
Lastly it was somewhat common (though never advised) for older implementations to edit theme files directly instead of creating overrides. Confirm this isn’t the case before starting otherwise you might lose any functionality implemented there.