If the distance from Earth / Milky Way Galaxy to the Andromeda Galaxy were a foot when the real distance is 2.5 million light years, then the 150,000 light year diameter Andromeda Galaxy would be the size of a dime and the Milky Way about 2/3 that size.
There are about 100 mostly small and few big galaxies within 2.5 million light years of us. You can see the Andromeda galaxy in a very dark sky with the naked eye a few times bigger than the moon’s apparent size.
The radius of the observable universe accounting for expansion of space isn’t 13.5 billion light years since the big bang but 46 billion light years. That’s only about 18,400 times the Andromeda distance, so it would be 3.5 miles in radius or 6.8 miles in radius about the size of a city center. That’s a big number but nowhere near infinity at that scale.
The volume of the sphere would be 26 trillion cubic feet, which you could compare with high estimates of the number of galaxies as 20 trillion.
The actual universe is larger than what is observable limited by the amount of space light can travel since the big bang, and no one knows if it is infinite or just really really big.