Hey! Here’s a good start:
I enjoy using a mix of Serebii and Bulbapedia, type “jigglypuff” for example into the search bar of Bulbapedia, scroll to the TCG article hyperlink and check each release to see the corresponding set, there’ll be a good register of each language that set was released in for international sets.
Also: This guide is the best around overall IMHO.
Hope this helps, happy collecting!