Hi Mallory P.,
You can use PfVf/Tf = PiVi/Ti, and since the pressure is constant, Pf = Pi, it becomes Vf/Tf = Vi/Ti, with Vi = 1.0 L and Ti = 283 K (273 K + 100), and Tf = 298 K. Solve for Vf, Vf = ViTf/Ti, or Vf = (1.0 L)(298 K)/(283 K).
I hope this helps, Joe.