Modal ontological argument

[Deesse23]

Answer: the future.

Literally, this is the geometric answer.

True, but, if the Universe's volume is finite at the beginning, then, it will remain so forever.  As such, distances on intergalactic scales are increasing, and, hence, so is its volume.

#1 It may finite, but it may not. In the latter case your point is moot
#2 Its expanding into nothing, meaning its just expanding. There is nothing it is expanding into.

When you blow up a balloon, the surface (rubber) just expands. It does not expand into any other surface, like space is not expanding into any space "external" to the universe.