I want to associate Term Store with the sitecollection that is migrated to new environment after migration. I have replicated the Term Store at destination, what now left is the association of the columns to the term store. If you have previously done the same or can give me an idea about doing it let me know.
You can use a Feature or manually connect the fields to the Term Stores in Managed Metadata Service Application. In feature-based approach, it can done in an Event Receiver for the feature. See this example 1 and example 2
How have you been doing it in old Farm?
If you go to Central Admin > Application management you will find a link called Service Application Association.
Make sure your web application is associated with the correct term store and associate it if not.
Once that is done, you can go to your web application > Site Settings > Term store management and check the term store association.
Once your terms are resolving correctly, you can check couple of metadata columns to see if its working or not.
By default if you are using the same term store as the source it should work without touching any of the columns. If term store is totally different you have to do lots of manual work.