Look, consciousness is a thorny problem. But then so is everything if you want to get into the weeds. Philosophically you can just about "prove" the axiom "There are thoughts." Even "I think therefore I am" is problematic because it presumes a distinct concept of self separate from the thought.
There are arguments to be made that consciousness isn't even a real thing, and that qualia are some sort of emergent phenomenon that exist only so much as a ship does - namely because we say they do.
...and yes, I went there. Ships don't exist, belonging to Theseus or otherwise. Ships are just labels we stick on collections of atoms, which themselves are labels we ascribe to collections of protons neutrons and electrons, which themselves are only collections of... and down and down we go. Maybe there's a most fundamental particle down there somewhere, but hell if we know what it is. Everything is just convenient labels because we don't have the capacity to deal with un-abstracted reality.
It all gets incredibly tedious terribly quickly, take it from one who spent 4 years getting a degree in this shit.
So how do you prove consciousness? You don't. There isn't a test for it, and there necessarily can't be because we can't even properly define it in ways that aren't circularly referential.
You pretty much have to treat the word "Conscious" like you treat the word "Pretty". You're not going to go out into the world and grind it up into constituent parts and sieve out the particles of attractiveness whereby something can have more or less of them, it's just a word that exists because we mostly agree on what it means not because it has a formal definition. I chose "Pretty" quite deliberately because across cultures and even individuals there can be really quite different opinions on that.