First import it all to unity. If the level is made up of several
objects then go to 'GameObject' at the top of the window and click
'Create empty'. Then drag and drop all of the other game objects into
that game object. Once you've done that go to the 'Project' tab and
click 'Create' and then 'Prefab'. Then drag and drop the game object
you made previously into that prefab and save le game.
Go to where you saved the whole project, get the prefab of the level
and upload that onto here and we will be able to import it directly to
unity.
Or upload the level to unity and send us the file in the assests
folder, but the previous way will make the folder smaller i believe.