I truly mean no disrespect, but before you can shoot 3,000 yards, you need to shoot 2,500 and before that 2,000 and 1,500... 1,000... 500... hell, 250.
Imagine if you could hold 1/2" groups at 100 yards. No small feat, but doable and not outside the realm of ordinary men. If you figured a 10% increase with each additional 100 yards, you'd be looking at something like 260 inch (yes, 21 foot) groups at 3,000 WITHOUT including any other error, like Coriolis Effect and spin drift.
Frankly, making reliable shots at 3,000 yards... at 2,000 yards... is beyond the ability that most any shooter could even train to achieve. Sure, there's men who could train to do it, pretty reliably. You've heard of at least a couple... Chris Kyle?
But, It's like asking "How do I become Derek Jeter?" You don't. If you were, you'd be out there with him.
If you plan to shoot at things that are 3,000 yards away, you'd better have money to burn, and I mean PILES of money to burn, and you better expect to miss A LOT. As in, if you ever do manage to hit the target, and by target I mean something the size of a house, it will be luck.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.