Define a text field and put it on your layout.
Show All Records
Put the cursor in this new field and select Replace Field Contents.
Use the calculation option with an expression such as:
GetAsText ( YourContainerField )
Note, the 'text' stored in a container field is usually the file path and file name of the inserted file if "store a reference" was specified. If these are text fields inserted as objects, manually double clicking the field record by record to open the embedded file is the only way that you can access the text in them. If they were inserted with "Store a reference", and they are text fields, you can try importing the data from these files into FileMaker, though that may have its own set of challenges to resolve.
I just need to say that one year ago, this fixed my problem immediately. I just had this same problem trying to figure out how to do this, and realized that I had already posted this question. Thank you SO MUCH for saving me hours and hours of copying and pasting.