Sorry, but is not possible to give you an exact answer since every situation is different.
For example, your apartment complex might be one story stand alone residences or an 8 story building. If your apartment is one story, Find My could likely show you where in the apartment the phone was located in relation to the outside walls and center of your apartment.
If you think that you left your phone in the pool area, and the general area has an open look to the sky, Find My might be able to show you the location of the phone within 10-15 feet.....unless the phone is at the bottom of the pool.
If the building is 8 stories, you will get general look from above, but it would not be possible for Find My to know which story or floor your apartment might be located on.