Changing Permalink Structure

[apexis]

Changing Permalink Structure
Hello ,

I have a question i am thinking about doing something but not sure if it will be a right move so basically
i want to change the link structure of my site for example this is the current link structure
www.example.com/how to do something/
now i want to change it to
www.example.com/category-name/how to do something

The reason why is because i have some backlinks on pages that i want to discount , i know that i can sent
the list of links to google for disavow but i want to make progress myself before sending the list of links .'

Now will this be a good idea to do ?
because all of the pages already indexed in google will now have a 404 error .
will it be something bad to do or should i not do that ?