I would like to know if there is a formula or a way to determine the amount of insulation a vacuum of 1 bar can produce. please note I am not talking about vacuum insulated panels.
1 Bar is the atmospheric pressure, i.e. it is not a vacuum at all.
But regardless of the pressure: no there is no formula. It is of course perfectly possible to calculate the heat transfer due to convection, conduction and radiation; but all of these will depend on the geometry and the materials used.