What form is needed to collect baggage in T3 then check into another airline also in T3

I need to travel from the US to Mongolia.
I must pick up my baggage in T3, then check in for my next flight to Mongolia also in T3 that leaves 4 hours later. I do not plan to leave the airport.
1. What arrival/entry form do I need to complete?
2. What is the process to collect my luggage and check into the next airline for the next flight?
3. How long does it usually take to collect my bags, go through immigrations, etc.? Is 4 hours enough time?