How can you catch Reshiram on Pokemon black if have any pokeballs or an action replay?

You can't catch Reshiram in Pokemon Black using normal Poke Balls or an Action Replay. Here's why:

* Reshiram is exclusive to Pokemon White: Reshiram is the legendary Pokemon featured in Pokemon White. It's not available in Pokemon Black.

* Action Replays are unreliable and potentially harmful: While Action Replays can be used to manipulate Pokemon games, using them to get Reshiram in Pokemon Black is unreliable and could potentially corrupt your save file.

* Trading is the only way: To get Reshiram, you'll need to trade with someone who has Pokemon White and has already caught Reshiram.

Therefore, there's no way to catch Reshiram in Pokemon Black through normal gameplay or with an Action Replay. Your best bet is to find someone willing to trade with you.