I’m assuming that you had the designer account that allowed you to export the code to another site. You won’t be able to perform a clean conversion from one site design template to another since they are each using their own “methods” to perform tasks. Here is how I would approach it;
Setup a local development enviroment similar to where you are hosting it and a wordpress environment.
Export the site from Webflow and get it 100% running locally as is, to insure that you have all of the code and assets that you need.
Create a written design template of how you want the site to look with the new changes. This will determine what you need to take from what you have and the new changes.
Create “blocks” from your existing site that can be used in Pinegrow as a new project.
Rebuild the site in PinegrowWP with the blocks and new modifications as you see fit.
Test the new site locally on several browsers and upload and test on your remote server.
Probably not what you wanted to hear but you won’t get a clean conversion without some tweaking. This way will allow you to test the changes before going live.