How can I display 2 fields in 1 line?

I want to ask for the identification number, In this case they should select Type of ID and then enter the number so the question should look like:

1.  ID:  _____  _________________________

Where the first line its a dropdown and the second one its a text line.

You can achieve that by shrinking the fields.

Drag a dropdown and a textbox field to your form and shrink them both so they are displayed in the same line:

If the textbox field for the ID number should be restricted to just numeric values, just set its VALIDATION property as NUMERIC. You may also use an INPUT MASK if you want to.

Related guide: Getting-Started-with-the-basics-of-Input-Masking 

Here's a quick form I came up with showing these https://form.jotform.com/62507818667972

You may clone it (here's how) so you can see how it was setup.