How many helium is in a liter?

The question seems to be asking about the amount of helium in a liter of gas. One liter of gas is a volume measurement, and it can contain different amounts of helium depending on the mixture. If you're asking about pure helium, one liter will contain one liter of helium gas at standard temperature and pressure. If it's a mixture, the helium content would be specified as a percentage or in terms of partial pressure.