Card order

Hi everyone! I have a newbie question 🙂

I ordered a “reading envelope” for fun off Etsy. I received it, all is well, three cards.

However, I am not sure which card would go in the card 1 position. The one in the back…. Or the one in the front when I opened it?

When I opened the flap, judgement was face up. I am not sure if it should be read as the final card of a three card spread, or as the first card. Any tips?