Basically, all the custom code and design are available in the app code and app design folder.
But you need to check if any change is available in the default Magento code.
If no change in the default Magento code then takes the zip of the app folder and database.
If change is available then take the zip of the app, vendor folder, and database.
One more thing the biggest size of the folder is the media folder so remove that folder and take the zip of the other folders and take the database backup.
then install those in your local system.
If my answer is helpful full then please set the accept solution flag and kudos flag so other members can take the same reference.
You can ignore generated folder as it will regenerate again by compiling and pub/media folder. Moreover, if your database size is too big then, you can ignore or remove all quote related tables.
When you export the database, you can delete the following tables.
Consider the above things and download the app folder and database zip file. That's it.
I hope this will help you to download your Magento store.
If not, feel free to contact us.
If worked, click KUDOS and accept as a solution.