Assuming a battery of 40 Ah,
it provides 12*40 = 480 wh, so with your 30x3 w = 90 w
you should be OK for 4 h on a battery.
It is better to be on the safe side and if you have 2-4, take them.
Now you need a regulator for the leds (current limit) , for the batteries (avoid deep discharge) , and for the solar panels ( avoid overcharge of the batteries).
All these will add some overhead on the power consumption.
What do you have ?