update text format "filtered html" on old nodes currently i have a content type with multiple nodes, that were created with a text format of plain text. is there any way to update all these nodes to be filtered html?

/admin/config/content/formats

i changed the default format to be filtered html, by making its weight -10 it is now at the top of the list. now when a user creates a new node it will have this format but how do i convert all the old ones?
Update the database directly using SQL queries. The queries are something like

UPDATE field_data_field_[example] SET field_[example]_format = '[text_format]';
UPDATE field_revision_field_[example] SET field_[example]_format = '[text_format]'


for a field named field_[example] that was created with the Field UI module and a text format with machine name [text_format]. Clear the cache afterwards.