Hi Becky,
Well, from Birth to Now for me would be a long time 62 1/2 years, so it would be a large book, I suppose.
For you it will hopefully be shorter.
I find outlines help a lot to focus my thinking when I write things.
For instance, I would put section titles based on Time
I. Birth (when, where, maybe who your parents are)
(write in some detail people have told you about your birth)
II. Baptism (if you were baptized as a baby, when, where)
This is when you became a Catholic - so say something about what you like about being Catholic, or about your sponsors (God Parents)
III. When did you start learning about being Catholic
(sunday school or confirmation class or do you remember going to Mass as a young girl - some details about what your learned about Jesus, about your Father in heaven, about the Holy Spirit, about Mass…When was your first Communion?
IV. If you are Confirmed, tell about that - if you remember the Bishop, what he said, or the promises you made - what did it feel like being an adult in the Church, even if you were young
V. I don’t know how old you are - if older, perhaps you are married or in college, have Catholic friends, whatever, do a section or paragraph about any of these things
If you write about 4 or 5 sentences (more or less) about each section, you will be telling the story of what Jesus and the Church have done in your life and what they mean to you.
That is what came to mind when I read your question. All the best, it should be a great retreat. Enjoy it, every bit of it.