If you are going to pirate something, at least make an effort to figure out how to work with the stuff you have. You can also ask us to clarify any error messages that you might encounter plus other questions you might have, but for the love of god, don't expect us to tell you how to use an emulator and a game from start to finish. It's not like it's going to blow up your computer if you happened to check the 'wrong' settings. If the emulator doesn't have any decent documentation, fiddle with the emulator anyway.
Continue from here by reading whatever documentation a given emulator has, and then fiddle around with the emulator itself, just to get a feel for it. What we can give you are the names of some of the more usable emulators for starters. Finally, open the Dreamcast emulator, it will ask you for the game file. Download the DC ROM of the game Street Fighter III: 3rd Strike from the download section.
Install the DC emulator compatible with your device. This isn't a place where give you step-by step instructions regarding every single detail, when it's clear that you haven't done done anything to help yourself. Download the Dreamcast emulator, there are versions for PC, Android, iOS and Mac. I know this may sound a bit cold-hearted, but if you don't know anything about emulation, then Dreamcast emulation is probably the last place for you to start. We don't need to know where you got the game, you don't have to tell us.
