If you were shrunk down to the size of an atom and wanted to travel to another galaxy, the distance you would have to cover would still be incredibly vast. Galaxies are typically separated by enormous distances measured in units of millions or billions of light-years.
The exact distance between galaxies can vary widely, as galaxies are not uniformly distributed throughout the universe. On average, however, the nearest large galaxy to our own Milky Way is the Andromeda Galaxy, located about 2.537 million light-years away.
A light-year is the distance light travels in one year, approximately 9.461 trillion kilometers (5.878 trillion miles). To put this into perspective, if you were traveling at the speed of light (which is currently considered impossible for massive objects), it would still take you 2.537 million years to reach the Andromeda Galaxy.
Keep in mind that this distance is for the closest galaxy to us. If you were to select a more distant galaxy, the distance you would need to travel as an atom would increase significantly.