Hello,
On futures with an amount of 100 USDT and by a leverage of 10 at currency pairs;
MATICUSDT , I opened a Long position at; 1.38, for a loss of 5 USDT on my
trade, what is the number of Stop Loss? A formula?

Thanks,

You are asking a question about basic risk. I will respectfully tell you that you should figure this out *before* you are trading with real money. Risk management is the best tool we have in our toolbox.