Where can I find this game? I assume its a emulator aswell.

Yes, unless you have an original Pokemon Mini and the game (both of which are very unlikely- the console is so obscure it isn't even listed on speedrun.com under "obscure consoles"), you use an emulator. The emulator I use is pokemini, which is the best emulator for the console. I don't think I can give you a link to the ROM, but just search "pokemon tetris rom". Good luck.

Yeah, I just ran across it on here yesterday. It looks like a neat little crossover game that I think could've been ported over to the GBC or maybe become an early GBA release.