Assuming you already have an MPPT controller rated for 35 amps or so, wire two new 100 watt ones in series and wire the existing ones in series too if they are not already. Then wire the two pairs in parallel. This will minimize voltage drop in the wiring from the solar port on the roof to the controller.
You will probably have to upgrade the wire from the controller to the battery to #6 gauge. Mount the two new panels the same as the existing, usually with aluminum feet, screws and Dicor sealant.
If your controller is a PWM type or it is not capable of 35 amps then replace it with a Renogy, Victron or Epever with a 40 amp rating.
David
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