"200x-1,20x1,20x7" doesn't look like a lot, I think it should be quite easy to recreate it manually in the editor.
But if you do have a big JSON file for a complex tilemap, you can edit the layout file in the project and paste it there.
Project folder\Layouts\LayoutName.json, search for the tilemap object name and you should be able to see similar tags, where you can copy/paste values.