Audio for jump scares is usually designed to support what is happening on the screen at the time. This means that, without more information, anything here will be abstract at best.
In making a horror sound, there are several elements that you could think about using when you're designing your own.
Shrill noises tend to upset humans: fingernails on a blackboard, a fork scraping a plate, the sound of subway wheels screeching, babies screaming, or if you're looking for something more musical, high and hard violins and woodwinds (Bernard Herman's score for Psycho).
Heavy thumping noises can introduce a sense of dread: taiko drums, stamping on floorboards, timpani drums, stampedes, large explosions, etc.
And finally, quick sharp cracking sounds can make us physically flinch or duck: doors slamming hard, whip cracks, a single gunshot, a single clap, fireworks, etc.
A mix of any or all of these will bring a reaction from your audience but, to make it work best, it should have a strong connection to what's happening in the picture and not just be a random scary sound.
Grab some sounds and experiment with different combinations. I would also recommend you watch some movies with jump scares you're trying to copy and see if you can figure out what sounds they've used.