Welcome to Five Head Island.  This pack uses the mod ex nihilo adscensio to gather most vanilla resources.  Ores drop from various mobs.  You can look up an ore or ingot and its tooltip will tell you what mob it drops from.  This book will help you get started with the mod.  More details can be gathered by using JEI, which you can see on the right of your inventory.  Most items have some sort of recipes, including items that normally spawn in the world.  Left-click on an item to see its recipe, and right-click to see its uses.