Bryan bought a total of 750 + 250 = <<750+250=1000>>1000 milliliters of milk from the two smaller bottles.
Since 1 liter is equal to 1000 milliliters, then 1000 milliliters is equal to 1000/1000 = <<1000/1000=1>>1 liter.
Therefore, Bryan bought a total of 2 + 1 = <<2+1=3>>3 liters of milk.
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