What do you mean by "Can we open the Scratch Jams?". Can you elaborate?
https://itch.io/docs/creators/game-jams This link tells you how to host a jam yourself. You will get some people to join through checking upcoming jams(I would recomend setting up the jam a month before it start but you can go shorter). If you really need to you could advertise it on discord, forms, your yt channel or anywhere else that you are allowed to advertise on.