Upgrading from 2.10 to 3.6 with Upgrade Tool

Hi, I’m trying to perform the above upgrade, but not doing well at all.
I’ve tried (a)copying my existing app to a new folder and running the upgrade tool on that folder, and also (b)installing 3.6 then copying the app folder from the 2.10 application into the 3.6 folder and running the update tool. Each approach gets me different syntax errors in the Cake code if I try to run the app.
Both approaches used upgrade all.
Is (a) or (b) the correct approach, or should I be doing something else please?

The upgrade tool only does the processes that can be automated and errors are to be expected. You then need to manually fix each error and do that changes that the upgrade tool could not do.

Thanks for responding. Errors are what I expected, but I expected Cake to throw errors in my app code, rather than syntax errors to be reported in Cake’s code.
Do you, or anyone else reading this, have any thoughts on whether my (a) or (b) approach should work?

Some Progress. I ran the update tool on a copy of the 2.10 app, but had to run each subcommand separately in the order in the update tool documentation, omitting skeleton and prefixed_templates. I then copied the app/src directory from the 2.10 app to the src directory on the new build 3.6.12 app. I now get a fatal error from a file in the src directory, which is much more what I expected.