how to transition ff_checkbox_group to pt_checkboxes?

Edit Subject

I've been working through the arduous process of upgrading an EE site from 1.6.8 to 2.1.3. Before making the EE version upgrade, I went ahead and upgraded Fieldframe 1.x to Matrix 2.1.2 in EE 1.6.8. Then, I updated EE to 2.1.3. I installed Matrix in the EE 2.1.3 control panel, but it did not automatically alter my fieldtypes. In other words ff_select did not become pt_dropdown, etc.

I was able to go into my database and manually alter the fieldtypes, and this fixed nearly everything. For some reason, neither ff_checkbox nor ff_checkbox_group translate to pt_checkboxes. If I open up an entry to edit it that I know has checkboxes selected, they do not appear selected on the edit entry screen. But if I look in the database field, I can see that there is checkbox data there.

For example, I have a list of checkbox options:
Hard Hat
Work Boots
Safety Glasses
Harness, Respirator

The data in the database looks like this when the first three are checked:
a:3:{i:0;s:8:"Hard Hat";i:1;s:10:"Work Boots";i:2;s:14:"Safety Glasses";}

If I open up an entry and check those three boxes and re-save, it alters the data in the database field to simply list the words on separate lines:
Hard Hat
Work Boots
Safety Glasses

Thus, it seems that ff_checkbox_group encoded the data differently than pt_checkboxes does.

Is there a way to manually prompt Matrix to process the fieldframe/matrix fields and update them to the proper current encoding? Or maybe I could run something through SQL to clear out the extra FF code.