How can I convert number field to text?

If I understand correctly, you want to change the number field of your form and use a text field instead? If that is the case, then unfortunately it is not possible to convert a number field into a text field. The only workaround would be to remove the number field and manually replace it with a text field.

not, I need convert numbers to letters, if you say is not posible but how can I use a java code or Github for sample:

https://eglador.wordpress.com/2013/02/27/conversion-de-numeros-a-letras-con-javascript/

https://gist.github.com/alfchee/e563340276f89b22042a

If you want to add the custom code from github into your form, then you will need to use the full source code of the form. Here's how: How to get the Full Source Code of your Form. Please let us know if you need further assistance. Regards.