We have an Umbraco which was developed by another agency. Unfortunately it seems they copied it from another Umbraco system they built for someone else and gave it away in this way to their current client. The problem with this approach is the document types names don't match the purpose for the business logic. For this reason I want to pull the data from this Umbraco 7 and then build another Umbraco (13/14 whichever is supported longest) with proper document types and names and then import data into the new version. How could I do this? Is it even possible?

The only thing that comes to mind that you could try is usync.migrations. Note I have not used it and can't validate it but maybe its a pointer in a direction you could try. https://github.com/Jumoo/uSyncMigrations

I’d worry about migrating the data first. Moving from MVC to Core requires quite an overhaul of any code base you are working with, and couple that with API changes between Umbraco 7 through 13 anyways… Yeah, I’d migrate things first. Keep their original names. Make sure the data migration goes well and nothing is left out that you absolutely need. Then back it up, and go to town. Rename what you need to rename. Refactor and migrate whatever code you need to. uSync Migrations is a good option. Though complicated sites on 7 prove time and time again to bring their own unique challenges 🙂

Depends on the data structure, how many doc types there are, how complex the data is (grid?, lots of custom properties?) and how heavily they are used. If there are 100-1000s of pages but 98% of them are say productPage and newBlogPostPage then it might just be worth writing a simple custom import yourself (API in v13 -> API in V7). If there are lots of complex data types then usync migrations will definitely help. If might be worth importing into a v13 even just to get it in using "old" doc types and then "importing" content to itself, e.g. creating new doctypes and structures and then running a few bits via the content service to map the data over.. Really depends on the original data structure, how much data there is and how complex it is to the best approach. But definitely sound out usync migrations first. Will save lots of time

Thanks, I've just realised there is a third-party plugin which builds some of the document types.... I'll give the above advice a go