i second Tim statement. You could look at this official documentation
https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/devenv-upgrade-v1-to-v2-overview
In my opinion, if you have just few extensions, I would do the following
- Create CSIDE table and table extension fields exactly the same as you have for your app v1 tables and move there all the data
- Recreate in CSIDE all your other objects you have within the app v1
- Remove completely your app v1 from the database (leave with no trace). Completely clean this out.
Now that everything is in CSIDE now, you could follow the path like any other customized NAV 2016 database by following this link
https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/upgrade/upgrade-overview-v15
Another thing that I would do, once you are in CSIDE, is to upgrade to version 14.x like any other customized CSIDE database.
Once there, use txt2al.exe to extract your private IP and transform that into an AL extension and move the data back from your CSIDE table facade into extension v2 tables.
When this step is done, delete the CSIDE tables and be sure that you have a not customized version 14.x but only standard code with your extension V2 (and data).
