Opening scene is the battle of Serenity Valley, it cuts away to the crew collecting illegal salvage and having a close call with the Alliance, they pick up Shephard and Simon as passengers / commuters on Persephone which I think is the scene you’re referring to.

The original pilot / first episode, Serenity (not to be confused as the movie of the same name), is an hour and a half long and sets up a ton of context for the rest of the show.

Instead, Fox aired the second episode, The Train Job, as a pilot.

Serenity was ultimately aired as a series finale / 11th episode, the show was cancelled before he three remaining episodes were aired.

If you haven’t seen Firefly, I strongly recommend that you start with the Serenity Episode. You’ll know by the end whether or not this show is for you.