That makes no sense.
If it was ancient Greek, considering it's written, it would have been "πυρά" that has "πυρές" as plural; obviously it is not.
If it was ancient Latin, it would have been "pyra" or "PYRA" as there is no capitalization rule for names here, with "pyrae" or "PYRAE" as plural. It could be medieval Latin, but then "Pyra" would be a reference to "the name of the place on Mount Œta where Hercules is said to have burned himself" so it's a proper noun and has no plural in English (there's only one, so there's no need or point in making a plural...).
Now,
considering you are writing in English and Pyra is the name of a product (a brand name, not a proper name), it gets its plural adding a "s", so you can buy three Pyras or three Dragonbox Pyras and take your Pyra to the park or wherever you want from September on.
en.wikipedia.org
Problem solved for English, courtesy of Mr. Huddleston & Mr. Pullum. For Czech, German, Chinese or whatever, you may want to check the grammar of those.