Nobody expects the new hire to be perfect. They expect you to say something when you’re not.

Competence is not really what you are being assessed on in the first weeks. Everybody knows you do not know the system yet, so the live question in people’s minds is whether you will flag it when you are stuck or quietly produce something wrong and hope. One of those is a training cost and the other is a problem.

Build the sentence now so it is ready: you are not sure about this and would rather check. Use it early, while it is still obviously reasonable. Nobody remembers the questions, and they do remember silence.