Convert Textarea to Writer + Update existing Content

I have an existing Website where I would like to convert a Textarea field into a Writer field.
Of course this is not a big deal for new content, but is there a way to convert all the existing content from many Pages?

At the moment I would probably just create a new Template for all the newly created pages and let the existing Pages still use the Textarea field. But maybe there is a simple solution to convert the content?

Thank you for any inputs!

Do you want to convert to blocks or to the writer field?

What sort of KirbyTags are you using in your textarea fields? Keep in mind that the writer field is not a replacement for the textarea field. It only supports a limited set of nodes.