A new 2010 SharePoint farm. Your upgrade strategy is "database attach".
[What you want]:
You want to install your old BDC files on the farm. And probably, you already know that BDC ADF files should be converted first in order to work on the new 2010 farm. So, probably you are looking for the easiest way to convert them.
[What you want to know]:
In case of "in-place upgrade" Business Data Catalog adf files will be converted automatically. How Business Connectivity Services upgrade works (in-place upgrade). Make a note that a backward-compatible Application Registry Service doesn't have UI interface to manage it.
In case of "database attach" upgrade strategy, you may have read that you can attach SSP database to migrate its content. Truth is: When you attach an SSP database, only your user profile store is upgraded. Search settings, Excel Service settings, Business Data Catalog (BDC) application definitions, and other settings must be recreated from scratch. Upgrading by using database attach (BDC)
You may have even discovered a lengthy MDSN article (How to: Manually Upgrade Business Data Catalog Application Definitions to Business Data Connectivity Models)that follow you through the whole experience with manually editing ADF file to convert it into a BDC Model. (BTW, still confused with BDC and BCS? - SharePoint 2010: BCS and BDC (Naming convention))
[What you want to do]:
My suggestion to you - " hybrid BDC upgrade approach". It's quite simple and probably you have already figured out).
The idea is to:
1. run "in-place upgrade" on some test 2007 farm with BDC files already installed there;
2. Export BDC Models from the upgraded farm.
3. Import them into a new fresh 2010 farm.
I see the most common scenario for "BDC Conversion into Models" as:
1. "Hybrid BDC upgrade approach"
2. Exporting the upgraded BDC models through SharePoint designer (SPD) 2010.
3. Creating a "Business Data Connectivity Model" project
4. Deploying a declarative BDC model with a feature in the new SharePoint 2010 farm.
Regarding details, refer to the material below.
[What you want to consider]:
My fresh experience with BDC upgrade is telling me that you can easily bump into some new errors that you haven't seen before since you have just started using SharePoint 2010.
My recommendation is to follow me. I am planing to get deeper with the BDC conversion and I will share my experience with you.
And some quick notes:
When to Use SharePoint Designer vs. Visual Studio When Building Solutions Using BCS
BDC MetaMan works with .Net connectivity , it won't help with declarative Business Data Catalogs.
The new project template "Business Data Connectivity Model" in Visual Studio 2010 will help you to package and deliver converted BDC. BUT, BDC Model designer in Visual Studio doesn't work with declarative BDC models, only .Net LobSystem,
You can import a model into the Project that was created by using other tools such as SharePoint Designer. You might choose to import an existing model to your project in the following situations:
To customize a model that is already deployed to a SharePoint server farm.
To package and deploy an existing model to multiple SharePoint server farms.
In this scenario this article is a great help - Deploying A Declarative BDC Model with a feature.