The concept of galaxies existing outside of our universe is not well-established within the current understanding of cosmology. The term "universe" typically refers to the entirety of space, time, matter, and energy as we know it. Our observable universe is the region of the universe that we can detect and study, limited by the distance that light has had time to travel since the Big Bang.
According to the current understanding, the observable universe has a finite size and is estimated to be about 93 billion light-years in diameter. This size is based on the current age of the universe, approximately 13.8 billion years, and the expansion of space over time.
However, it is important to note that the term "universe" can sometimes be used differently in the context of speculative theories, such as multiverse theories, where the idea of multiple universes or other regions of space-time beyond our observable universe is considered. These speculative theories are not yet firmly supported by observational evidence and are actively researched and debated in the field of theoretical physics.
In summary, galaxies are primarily understood to exist within our observable universe, and their distances from us are measured in terms of billions or millions of light-years. The concept of galaxies existing outside of our universe or the distances to such galaxies is not currently supported by empirical evidence or widely accepted scientific theories.