# a land in which you will not eat bread in poverty

"a land where there will be plenty of food for you". This means that they will eat and they will not be in poverty. They will have plenty to eat. The word "bread" refers to food in general.

# and in which you will not lack anything

"and where you will have everything you need" 

# stones are made of iron

The stones are full of iron ore. Iron is a very hard metal useful for making swords and plows.

# dig copper

"mine copper." Copper is a soft metal useful for making household utensils.