The future perfect tense is used to describe actions that will be completed at some point in the future. It is formed with "will have" + the past participle of the verb.
The sentence "I shall be telling you three stories." is in the future continuous tense. To convert it into the future perfect tense:
\[
\text{Future Perfect Tense:} \, \text{I shall have told you three stories.}
\]
% Final Answer
Final Answer:
The sentence in future perfect tense is: I shall have told you three stories.