Merge folders from 2 accounts and block future emails from one account

My deceased friend had thousands of emails that I reviewed and put into folders.

I alerted all of his contacts to stop using this account and he currently receives nothing but multiple spam emails per day.

I want to stop seeing his emails but I want to save the folders that I created.

His wife has a different comcast.net email address and I would like to move his folders in with hers.

How can I do that such that I can 1. access both his and her folders 2. continue to receive her emails and 3. stop receiving his emails?

I usually use Chrome for both of them but I am open to using Thunderbird.