Note I already know its probably in the AppData folder but what folder/files store it?
I haven't looked specifically in any files yet
HTTP Toolkit is an Electron app, and this data is stored in local storage & similar web API mechanisms inside the app's state. There's no specific file where that lives, and any access is likely to require a complex extraction process from within Chromium's internal storage of this state. The state itself is raw JavaScript objects too, not a standard serialized format that you'll be able to read easily.
This data is probably not practically accessible from disk.
If you want to access this, the best option is to export it from the UI directly. For the Send requests, you can do this by sending any request, and then exporting the resulting request & response as a HAR directly from the View page, or exporting the request itself from there as ready-to-run code snippet.
It would be interesting to expose options to export these tabs more directly - since HTTP Toolkit is open source, I'd suggest opening an issue at github.com/httptoolkit/httptoolkit with more details, or you can even add open a PR to add this yourself and get free Pro in return as a project contributor, if you're particularly keen to make this happen.