This is an example of a double replacement reaction
Barium oxalate has a solubilit of 0.929 mg/L
Sodium nitrate has a solubility of 91.2g/100mL at
Looking up solubility data allows you to figure out which product is not soluble in water. Every chem student should memorize that nitrate compounds are always soluble in water.
This video covers the topic of how you can predict products of reactions if you are only told what the reactants are.
This video provides an explanation of the process of writing a net ionic equation.
Hope this helps