hopefully, I manage to explain this well.

The way I have seen it done is to divide the graphics into tiles (in this example 32x32), remove duplicates, and piece them together in the game engine to save resources and file size.

Typically, making tiles square is recommended as it makes it easier to work with grids in game engines.

example: The pink rectangle would represent the tile below it as the tile you save, then the down arrows would be where a copy of that single tile would go when reassembling the full graphic in engine.  the same process would apply to all tiles, and each frame would have the same treatment.

you can export them all on a single png as a tile sheet, especially since the tiles all go together, but you would want to organize them in a way that makes it easy for people to know what tile goes where.

Since there are three frames you can group the 32x32 tiles so the frames are together. so the tile under the pink box I made earlier which would be a tile from frame 1 could be placed then have the same tile but from frame 2, and then the tile from frame 3. That way it can be organized.

the first image is a Super Mario world tile sheet from spriter's resource, it shows animated sprite objects and is organized in a way that makes it easy to see which frames each object has, and in what order. this general sort of layout is what I generally feel looks the best, but it doesn't have to be exact, as long as its organized well.

the second image is a tile sheet that shows the darker colored wood pieces on the left, then the lighter wood next to it to show that it's grouped, and then the other tiles such as the animated fire or cannons are laid out in a way to show the proper animation order and to keep them grouped together.