Upgrade Concrete to current

I am completely new to Concrete5. I have a new customer that has come to me with an old website version, and I would like to try to upgrade it to the current version. I have read through some of the documentation and made one failed attempt. The documentation mostly talks about upgrading from much more recent versions. I'm looking for advice on how to proceed, if it is feasible, will the theme need to be rebuilt, and any other suggestions or advice.

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c5hub replied on at Permalink Reply
There is not an upgrade path from 5.6 to the latest version unfortunately.

There were breaking changes several years ago across versions which means there is no automatic way to achieve this.

No 5.6 themes or add-ons will work with the latest version, so you'd be best to rebuild the entire site on the latest version, including re-building the theme, or purchasing one from the marketplace.
JohntheFish replied on at Permalink Reply
The best you can achieve through upgrades is c5.6.4, which is the final version of the 5.6 legacy code. 5.6.4 is stable and compliant with latest php versions, but will not be further developed.
andrewjaff replied on at Permalink Reply
You will have to rebuilt the site in current version. Theme and addon also have to modify, if that is not available for current version.