"who will own what you have stored up?" or "who will have what you prepared?" This is a rhetorical questions intended to make the man realize that he would not longer possess those things. (See: [[rc://en/ta/man/translate/figs-rquestion]])
## stores up treasures ##
"saves up valuable things"
## not rich ##
"poor" or "stingy" or "not generous"
## towards God ##
This could be translated as "in the view of God" or "in relation to God." The meaning is that this person has not invested in the things that are important to God, or that God will reward.