Crock Pot to Enameled Cast Iron Pot Cooking Times and Temperatures
You don't need to convert, because you can't overcook it. 

Very briefly, because it has been discussed in many other places: there are types of meat which can be overcooked and types which can't. All recipes for crockpots are made from the type of meat which can't be overcooked. So you don't have to worry about cooking it too long. You just cook it for as many hours as you have time to wait for it. If you want to, you can leave it in for the same time as in the crock pot. 

As for the temperature, you choose one which will allow for a slight simmer. It will be different depending on your oven (they are never accurate) and the amount and shape of the thermal mass inside (dutch oven + food). The first time, set it rather high (maybe try the 325 you saw in recommendations), and check on it every 20-30 minutes. Once it has reached 80 Celsius internal or above (or look for a slight simmer if you don't have a thermometer), turn the heat down by 50 F. Continue until simmer has stopped, then go back up 50 F. Next time set this temp from the beginning. You might want to heat the stew quickly on the stove first, then put it in the oven at the optimum temperature, else it will take ages just warming up in the oven.