A criminal background is a criminal background. If you were prosecuted in the same judicial circuit as you’re applying for a job, it’ll show up whether it was last week or twenty years ago. This is a general rule, but your circuit may have a lower-tech database, or no electronic database at all, in which case old cases may be difficult to track down.
If the crime was in another jurisdiction, it won’t show up on a really quick check, but most employers go deeper in a background check. If the crime was unrelated to your position, though, or was relatively minor, it might not even make a difference.