To use jUpgradePro v3.8, you should install first a new fresh Joomla! 3.8+ without any content sample data. This will be the new site that you can migrate the data from your old site and configure a new version of your Joomla! site.
A new functionality of jUpgradePro is that could be used to move data between same versions too. So this extension is not only used to migrate data, also could be used to move data between Joomla! sites.
1.0 |–––––––––> 2.5, 3.0+
1.5 |–––––––––> 2.5, 3.0+
2.5 |–––––––––> 2.5, 3.0+
3.0+ |–––––––––> 2.5, 3.0+
jUpgradePro has two method to migrate your data:
This is the common method, you should set into the configuration your MySQL credentials and server host name, then jUpgradePro will to retrieve the data using the MySQL functions.
Pros: Its more faster than RESTful.
Cons: You must to have the MySQL credential access to use it.
This method use webservices calls to get your old data from your Joomla! site. It needs to install a plugin into your old site that 'serve' the RESTful responses to the 'client' that is the Joomla! 2.5 or 3.0+ site.
Pros: More easy to configure. More directly data move.
Cons: A little bit slow.