Can you clarify so we can better help without making potentially bad assumptions?
It sounds like you have a game that was previously downloaded on a older iPad with 256GB storage, but you now want to install it on a different iPad that has 64GB. Am I reading this correctly?
Launch the iOS App Store app and find the game. Look in the "Information" section of the game's page to see the size:

What we do not know is if this is the size of the download of a compressed installer, or the actual size of the ready-to-use game.
We do know that, in addition to the app itself, games tend to have support files with data including level history, achievements, and scores. That adds to the storage depending on how efficiently the app is coded.
You can also contact the game developer. They know better than anyone what space the game and its support files requires .
How to contact an app developer - Apple Support