rom edit I want to make a diorama but I don't know where to get the sprites

[Vidit]

 

I know that GUMY art and others have pdf templates but I would rather download the sprites myself and make it , can someone tell me where to get the sprites like in GUMY art's video he used the professor oak's lab which had no objects how do I get that or how can I make that? If there a way to extract assets or tiles from the game itself(the game I am looking to extract from is Pokemon fire red or lead green) then Please help