I'm going to be sloppy with this argument but you'll get the idea behind it I hope.
Work is energy, it has units of joules.
W = - P(deltaV)
If you look at the units on that you get,
J = atm*L
With the appropirate values for your conversion factor you can convert the standard L*atm/K mol gas equation to J/K mol.
Like I said, this is sloppy and incomplete so let me know if you need clarification or want more information.