how can i mask

There are a lot of scenarios where you can you masking with Jotform. Most common scenarios are found on this article.

https://www.jotform.com/help/381-Getting-Started-with-the-Basics-of-Input-Masking

It also teaches you how to mask, depending on which scenario you wanted.

Also, we have an advanced topic about masking, which might come in handy for you. Here's the link

https://www.jotform.com/help/358-How-to-Set-Content-Mask-on-a-Form-Field-Based-on-Another-Field-Input

Hope that helps. Let me know if you have any other concerns.