Begin the second part of the sentence with the phrase, “…but I don’t know…” Write whatever comes to mind. If the second part of the sentence doesn’t seem related to the first part, don’t worry about it.
It might help to think about words that commonly follow the word know. Words like who, what, when, where, why, if, that, how…
After you have filled a page, go back through what you have written. Put a question mark over the things you don’t know but wish you did. Put a smiley face over the things that you are glad you don’t know. Are there things that get no mark?
When you have finished be sure to give your work a title.
Here is a more detailed version of these directions.