You need to add funds in advance, and make sure roaming is enabled. Some have posted it didn’t work in a covered country and they had to buy a local sim. But the local sim was cheaper than day pass anyway.
You would need to have additional funds on the account for the amount of time you would plan to use. Here is a link: https://www.verizonwireless.com/support/prepaid-international-faqs/#travelpass1 , with more information. JesseM_VZW