The time it takes to upgrade an Odoo instance from version 13 to version 16 will depend on several factors, such as the size of the database, the number and complexity of the installed modules, and the availability of the necessary resources (e.g. server resources, network bandwidth, etc.).

In general, it is recommended to perform a full backup of the Odoo instance and its database before starting the upgrade process. This will allow you to restore the instance to its previous state in case any issues or errors occur during the upgrade process.

Once the backup is done, you can start the upgrade process by following the steps outlined in the official Odoo documentation. In general, the steps to upgrade an Odoo instance from version 13 to version 16 are as follows:

1. Stop the Odoo service.

2. Install the necessary dependencies and libraries, such as the Python package manager (pip) and the PostgreSQL client (psql).

3. Download the latest version of Odoo (version 16) from the official Odoo website.

4. Extract the downloaded file and copy the extracted files to the appropriate location on the server.

5. Update the configuration files (e.g. odoo.conf) to reflect the changes in the new version of Odoo.

6. Run the upgrade script (odoo-upgrade) to upgrade the database schema and update the installed modules.

7. Start the Odoo service and verify that the instance is running correctly with the new version of Odoo.

After completing these steps, the Odoo instance should be upgraded to version 16, and all the standard modules should be available and working correctly.

Alternatively, you can also export the documents from the Odoo 13 instance and then import them into the Odoo 16 instance. This will allow you to migrate the data and documents from the old instance to the new instance without having to perform the full upgrade process. However, this approach may not be suitable for all cases, and you should carefully evaluate the pros and cons of this approach before deciding to use it.

Thank you. Is there any documentation on this?
Do I also need to export/import the systemdocuments?