What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
This can either be done through mask - by forcing the input to be a 3 digit number and using sub label to explain that leading zeros should be added, or to use the conditions to add the zeros to the value entered in some other field.
You can see this in a quick demo here: https://form.jotform.com/60334978432965
You can see how both are done by cloning the form to your own account following steps here: How to Clone an Existing Form from a URL or by asking more here and we would be happy to explain each.