If you have a lot of entities and doing it by hand is not an option, you could try and learn how to execute editor scripts in the browser console.
That way you could read the JSON data, loop through it and recreate the entities. For the components you can do the same, though it can be a bit harder learning to do that.
This thread contains info on how to get started with that, it may be old but most of the things are still the same. Note the editor API is unofficial and not supported, so be careful when using it (there is work in progress to release an official supported version):