Scripts

In the second table, the creature ID will be the key, and the fields will represent the conversion cost. After determining, based on the first table, which creature needs to be converted into (we obtain its ID), we find the conversion cost in the second table using that ID.

If the window with multiple answer options doesn't work for you (see the FAQ by Jack_of_Shadows), then it won't be possible to implement a proper selection between multiple options.