Translation:Tell me what you think of my poems, Anna.
"Penser à" and "penser de" have different usages. "Penser de" refers to having an opinion about something or someone, which is the correct usage in this particular exercise. "Penser à" refers to having someone or something in mind more generally. For example:
"I am thinking about you" = "Je pense à toi"
"I think well of you" or "I have a good opinion of you" = "Je pense du bien de toi"
As another example, if you wanted to say "Think about my poems, Anna", that would use "penser à": "Pense à mes poèmes, Anna."