A stackable pair ... meaning a frontload washer with a dryer set on top that can also be separated and run in side-by-side orientation?

Or a stacked pair, meaning a unitary machine that can comprise either a frontload or a topload washer, with dryer at the top, and can't be run separated?

Model number(s) of the machine would clarify your situation.

Separate machines. My dryer is dying, but my washer still works. They must be 24" because I have a finite amount of space.