The conversion factor from deli liters (dL) to liters (L) is:

$$1\text{ dL}=0.1\text{ L}$$

If you wish to convert a certain number of deli liters to liters, multiply that number by 0.1. For example, $250\text{ dL}=\frac{250\cancel{\text{ dL}}}{1}(0.1\text{ L}) = 25\text{ L}$