Is it possible to add captcha to Moto CMS 3 templates ?

Unfortunately, there is no CAPTCHA feature in pre-installed MotoCMS contact forms. However, you can get Advanced Contact Form widget. This widget lets you add Google CAPTCHA, many other fields like dropdown menu, radio buttons and checkboxes.
Learn more about Advanced Contact Form here.
You can check this video tutorial on adding captcha to your Advanced Contact Form widget.