To have Cydia you need to be jailbroken.
To be jailbroken you need to be on a firmware that is jailbreakable AND have a model of iPhone that the jailbreak will work on.
You have neither.
iPhone 5 is 32-bit. The last 32-bit jailbreak was for iOS 9.1.
iOS 10.3.3 is not jailbreakable. If it was, you'd still have a 32-bit device that cannot be jailbroken.
Not going to happen either way.
Anything you find that says so is fake.